(See Energy Level Diagrams for 12C)
GENERAL: See also (1975AJ02) and Table 12.7 [Table of Energy Levels] (in PDF or PS).
Shell model: (1974BOZB, 1975BI05, 1975BO27, 1975FR06, 1975GI1C, 1975MU13, 1975WA30, 1976BA24, 1977CA02, 1977CA08, 1977GR02, 1977JA14, 1978FU13, 1978MU04, 1978SV01, 1979LO1F).
Collective and deformed models: (1974BOZB, 1975BO27, 1975KI21, 1975LE14, 1975MC15, 1975SO07, 1976GL1C, 1976PA25, 1977CA08, 1977TH03, 1977UE01, 1977VI03, 1979MA1J).
Cluster and alpha particle models: (1974AG06, 1975AB1E, 1975BA16, 1975HO1E, 1975IN04, 1975KA29, 1975KR1D, 1975KU1N, 1975NE1B, 1975RO1B, 1975WA30, 1976CA05, 1976FL1B, 1976FU1G, 1976HA09, 1976HO1F, 1976HO1A, 1976KA14, 1976KI16, 1976SA1F, 1976VA21, 1977AG03, 1977BA76, 1977BE49, 1977FU1E, 1977HO1E, 1977HO1F, 1977KA1U, 1977KA1Q, 1977KH02, 1977MY1A, 1977MY1B, 1977NA13, 1977SA19, 1977SA1C, 1977TA1J, 1977TA1K, 1977UE01, 1977UE1B, 1978AR1H, 1978DZ01, 1978HO1E, 1978HU09, 1978IS04, 1978MA1U, 1978OG1A, 1978OS01, 1978UE1B, 1979GO1P, 1979HE1G, 1979KA1P).
Special levels: (1974BOZB, 1975BA16, 1975HO1E, 1975IM02, 1975MC16, 1975NA21, 1975NG1A, 1976BA24, 1976FU1G, 1976GA16, 1976GL09, 1976GO1J, 1976HA09, 1976HO1A, 1976IR1B, 1976KI01, 1976VA21, 1977BA76, 1977CA08, 1977GR02, 1977GR24, 1977JA14, 1977KA1Q, 1977KN03, 1977MO1Q, 1977SA17, 1977TA1J, 1977UE01, 1977UE1B, 1978AR1H, 1978BA31, 1978BE56, 1978GO1K, 1978HO1E, 1978HU09, 1978LA1D, 1978MC04, 1978MI04, 1978RO17, 1978SH04, 1979DU1E, 1979HA1E, 1979PO03).
Electromagnetic transitions: (1974BOZB, 1974HA1C, 1975BE24, 1975BI05, 1975BO27, 1975DO1D, 1975KA29, 1975MC16, 1976KI01, 1976VO1C, 1977AG03, 1977BE49, 1977DE15, 1977DO06, 1977FU1E, 1977GR02, 1977GR24, 1977KA1Q, 1977MA1Y, 1977MY1B, 1977YO1D, 1978AR1H, 1978FU13, 1978GO1K, 1978KI08, 1978MU04, 1978MY1B, 1978UE1B, 1979MO07, 1979MO1U, 1979MO1X, 1979PO03).
Giant resonances: (1974HA1C, 1975CO1E, 1975DO10, 1975GE1K, 1975GO22, 1975MC15, 1976BE1P, 1976KO1G, 1976MS01, 1977DE15, 1977GO1F, 1977KN03, 1977MA2E, 1977SA1Q, 1979DE1T, 1979GO1Q).
Special reactions: (1975AB1D, 1975AL04, 1975AR14, 1975FA1D, 1975GR13, 1975HU14, 1975KO1F, 1975ME1F, 1975PE03, 1975RE08, 1976AB04, 1976BA08, 1976BE1K, 1976BO1N, 1976BU16, 1976CH28, 1976DA1G, 1976EG02, 1976FR05, 1976HE1H, 1976HI05, 1976HI01, 1976HO1D, 1976LE12, 1976LE1F, 1977AR06, 1977BU07, 1977CE1B, 1977FE1B, 1977GE08, 1977GO07, 1977HA18, 1977HO27, 1977JA1J, 1977KA1P, 1977KO1Y, 1977KU1D, 1977LI1J, 1977MA1U, 1977MA1W, 1977NA03, 1977PR05, 1977RE08, 1977SH1D, 1977ST1J, 1977ST1G, 1977TO1G, 1977UD1A, 1977VA02, 1977YA1B, 1978AB08, 1978BA24, 1978BH03, 1978BI03, 1978BI08, 1978DI04, 1978FU1H, 1978GE1F, 1978GE1C, 1978GO1N, 1978GR1F, 1978HE1J, 1978HE1C, 1978KO01, 1978LE15, 1978OB01, 1978TU06, 1978VO1D, 1978VO1A, 1978WE1D, 1978WI1G, 1979AL1H, 1979CH06, 1979DU1E, 1979DY01, 1979GA04, 1979GO11, 1979HA1E, 1979PO10, 1979SC08, 1979SI1A, 1979SI09, 1979WA1H, 1979WE06).
Applied topics: (1975BE1U, 1975GA1E, 1976EC1B, 1976LE1Q, 1976SC1G, 1977BE2F, 1977FI1A, 1977MO1B, AN78E, 1978HE1K, 1978KE1E, 1978LE1P, 1978NA21, 1978TR1E, 1979AN1L, 1979EN1D, 1979GR1E, 1981JA1H).
Muon and neutrino capture and reactions: (1974EN10, 1974KO1H, 1974WA1C, 1975BA40, 1975BA56, 1975CH22, 1975DO1F, 1975DO10, 1975DO1D, 1975FE1B, 1975GE1E, 1975IM02, 1975KI2A, 1976DA1H, 1976DO1J, 1976HO1G, 1976SU03, 1977BA1P, 1977BO2C, 1977BR1K, 1977CA1M, 1977DO06, 1977HW01, 1977LE1K, 1977MU1A, 1977PO1B, 1977PR1B, 1977WA1F, 1977WA1G, 1978BA1G, 1978BA57, 1978BR1C, 1978DE15, 1978GU05, 1978HW1A, 1978KO31, 1978MU04, 1978PA06, 1978PA1F, 1978SE1B, 1978WU01, 1979BE1N, 1979DE01, 1979DO1C, 1979FI1E, 1979PA1J, 1979PR1D, 1979RO03, 1979RO1H, 1979TR05, 1979VE1D).
Pion capture and pion reactions (See also reactions 39 and46.): (1973BA1M, 1974AR1E, 1974AZ1B, 1974AZ1C, 1974BO1D, 1974BO1Y, 1974CAZD, 1974GR1K, 1974LU1D, 1974SP1A, 1974ST1K, 1975AB12, 1975AL1E, 1975AM03, 1975AN1L, 1975AZ1C, 1975AZ1D, 1975BA14, 1975BA1L, 1975BA54, 1975BA1G, 1975BA66, 1975BA1P, 1975BA57, 1975BA1W, 1975BH03, 1975BO1B, 1975BR1H, 1975BR1D, 1975BR1K, 1975BU1E, 1975BU1A, 1975BU1G, 1975CA17, 1975CA31, 1975CE03, 1975CO06, 1975CO1G, 1975DR02, 1975DU06, 1975DU1A, 1975EI1A, 1975EI1B, 1975ER08, 1975FU07, 1975GA08, 1975GI09, 1975GI13, 1975HE06, 1975HU1D, 1975HU13, 1975IN1B, 1975JU02, 1975KA03, 1975KA1G, 1975KI1E, 1975KO1F, 1975KO25, 1975KU02, 1975LO1F, 1975MA1M, 1975NA08, 1975NA16, 1975NI1B, 1975PA1D, 1975PE1C, 1975RA1N, 1975RO11, 1975RO1G, 1975SC1V, 1975SC1N, 1975SH1D, 1975SH17, 1975SI10, 1975SI18, 1975SI1E, 1975ST1G, 1975TA1C, 1975TO10, 1975VA1D, 1975VE05, 1975VO1D, 1975WA1H, 1975WA1J, 1976AL1J, 1976AL1K, 1976AS1B, 1976AZ1A, 1976BA1V, 1976BA1X, 1976BA47, 1976BAYQ, 1976BAYR, 1976BE39, 1976BE1K, 1976BO1P, 1976BO1K, 1976BR1M, 1976BR1N, 1976BU1F, 1976BU1D, 1976CA01, 1976CA23, 1976CA1H, 1976CH1H, 1976CHZW, 1976CO10, 1976CO13, 1976DO1D, 1976DO06, 1976DRZS, 1976DU1B, 1976DU1F, 1976ED1A, 1976EI1B, 1976EN02, 1976FR14, 1976FU1E, 1976GI1E, 1976GU17, 1976IV03, 1976KA02, 1976KI1E, 1976KI1H, 1976KI07, 1976LE02, 1976LE1P, 1976LI24, 1976LI26, 1976LO1C, 1976MA48, 1976MAYT, 1976MI14, 1976NA16, 1976NI02, 1976OS03, 1976PI1B, 1976PI12, 1976RO14, 1976SR1A, 1976TA1E, 1976TH09, 1976TR1A, 1976VA1F, 1976WA10, 1976WA07, 1977AB09, 1977AH04, 1977AL15, 1977AL1C, 1977AL1V, 1977AN1H, 1977AN1J, 1977AN1K, 1977AP1A, 1977AP1B, 1977AR1F, 1977AR1J, 1977AU1G, 1977AU1H, 1977BA60, 1977BA2H, 1977BA51, 1977BA1Q, 1977BA2G, 1977BA2Q, 1977BA2R, 1977BA73, 1977BA2V, 1977BE2K, 1977BE35, 1977BE69, 1977BEZY, 1977BO05, 1977BO1X, 1977BO1E, 1977BO1Y, 1976BR1L, 1977BU25, 1977BU1K, 1977BU1L, 1977CH1N, 1977CO1N, 1977DI03, 1977DI1B, 1977DO06, 1977DR1E, 1977DY02, 1977EI1A, 1977ER1A, 1977ER1B, 1977FR09, 1977FU11, 1977FY1A, 1977GE04, 1977GE1D, 1977GI06, 1977GI14, 1977GR1G, 1977HA1U, 1977HA1V, 1977HI1E, 1977HO1B, 1977JA1G, 1977KA1N, 1977KI1L, 1977KO25, 1977KU1G, 1977LE1H, 1977LE1G, 1977LI11, 1977MA1R, 1977MA1M, 1977MA2C, 1977MA35, 1977MC1E, 1977MO12, 1977NA02, 1977NA1K, 1977NA1L, 1977NA1M, 1977OH1B, 1977PI1D, 1977PI02, 1977PI1E, 1977PI09, 1977PR1G, 1977RA1A, 1977RO21, 1977RO25, 1977SC1F, 1977SE13, 1977SH14, 1977SI01, 1977SM06, 1977SP1B, 1977ST09, 1977ST1G, 1977TH1F, 1977VI1A, 1977WA1H, 1977WE1J, 1977WI1E, 1978AL1N, 1978AM01, 1978AN1E, 1978AN2B, 1978AN1F, 1978AN1G, 1978AN1H, 1978AR08, 1978AR18, 1978AZ1C, 1978AZ1D, 1978AZ02, 1978BA50, 1978BA1Y, 1978BA1T, 1978BE1N, 1978BE64, 1978BE1X, 1978BE27, 1978BH01, 1978BL1B, 1978BO01, 1978BO1P, 1978BO25, 1978BO26, 1978BR1J, 1978BR1K, 1978BU1J, 1978BU1L, 1978CH1V, 1978CO02, 1978CO16, 1978DO07, 1978DY01, 1978EI1A, 1978EP01, 1978EP02, 1978ER1C, 1978FU04, 1978FU09, 1978GA1D, 1978GA11, 1978GI01, 1978GI05, 1978GI14, 1978HA34, 1978HA1V, 1978HA37, 1978HI03, 1978JA09, 1978JA1G, 1978JO03, 1978JO09, 1978KI08, 1978KL06, 1978KO34, 1978KW1A, 1978LA1L, 1978LA08, 1978LI1E, 1978MA1T, 1978MA1J, 1978ME05, 1978ME1F, 1978MI02, 1978MO01, 1978MO25, 1978MO23, 1978NA1N, 1978PA14, 1978PE1D, 1978PE11, 1978PE12, 1978RO1J, 1978RO16, 1978RO1H, 1978SC1G, 1978SC1H, 1978SE07, 1978SI1E, 1978SI1D, 1978SP06, 1978TA1L, 1978TH1C, 1978TH1D, 1978VL1B, 1978WA1B, 1978WE1H, 1978WO11, 1978YO1D, 1978YO02, 1979AL1T, 1979AL1U, 1979AM1D, 1979AN1J, 1979AN1K, 1979AR1H, 1979AR1K, 1979BA04, 1979BA16, 1979BA2G, 1979BA1M, 1979BA2H, 1979BE1N, 1979BL1H, 1979BO1B, 1979BO1Y, 1979BO1U, 1979BO12, 1979BO23, 1979BO2D, 1979BO2E, 1979BOZW, 1979BR1F, 1979BU1K, 1979BU1D, 1979CE1A, 1979CH1P, 1979CH06, 1979CH05, 1979CH1U, 1979CH1V, 1979CH1W, 1979CO1L, 1979CO1M, 1979CO1H, 1979CO1N, 1979CR1E, 1979DA1J, 1979DA1L, 1979DE06, 1979DE1U, 1979DI1A, 1979DY02, 1979EI1A, 1979EL1E, 1979EN1E, 1979GA08, 1979GU01, 1979GY1A, 1979GY1B, 1979HA07, 1979HO1F, 1979HU02, 1979JA1K, 1979KL1D, 1979KL1E, 1979KL1F, 1979KL1G, 1979KN1E, 1979KU1J, 1979LA02, 1979LA1M, 1979LU1C, 1979MA07, 1979MA1P, 1979MA2H, 1979MA2J, 1979MI06, 1979MIZV, 1979MIZX, 1979MO1V, 1979MO1W, 1979NA1M, 1979NA1N, 1979NA1P, 1979NA1E, 1979OH1A, 1979OH1C, 1979PEZX, 1979PI1G, 1979PR1D, 1979RE1A, 1979SA1P, 1979SC02, 1979SC1J, 1979SH1M, 1979SH1N, 1979SH1P, 1979SH1Q, 1979SI1F, 1979SO1D, 1979ST02, 1979ST1N, 1979STZO, 1979TA1J, 1979WA1J, 1979WI1A, 1979WI1J, 1979WU07, 1979ZI1C).
Reactions involving antiprotons: (1977RO23, 1977WE1E, 1978YO02).
Kaon capture and reactions involving kaons and other mesons: (1974BO1Y, 1975DU1A, 1975PN1A, 1975PO1C, 1975TA1C, 1975VA1C, 1976AR1K, 1976BO1P, 1976BO1K, 1976BR1G, 1976DE1D, 1976EI1A, 1976KI1E, 1976KI1G, 1977BO2C, 1977CO04, 1977DO11, 1977JU1C, 1977PO1A, 1977TH1D, 1978AL04, 1978AT01, 1978BA1W, 1978BO1P, 1978BR1G, 1978DA1A, 1978EP02, 1978HE02, 1978KW1A, 1978PO1A, 1978SC1G, 1978TH1E, 1979BE2G, 1979BE2H, 1979BO12, 1979DA1K, 1979DO05, 1979GA1D, 1979KI1C, 1979MA2F, 1979MA2G, 1979PO1D, 1979WA1J).
Other topics: (1974BO1Y, 1974ZU1A, 1975BE48, 1975BL1E, 1975CA1N, 1975FA03, 1975FR06, 1975GA1G, 1975HO1E, 1975KO1C, 1975LE1E, 1975MU13, 1975PN1A, 1975PO1C, 1975SC1M, 1975SO04, 1975SO07, 1976BR1G, 1976DA1E, 1976ES1A, 1976GL09, 1976HA09, 1976IR1B, 1976KH04, 1976KI01, 1976KI16, 1976LO1D, 1976MA04, 1976SA16, 1976ST13, 1976VA1C, 1977BO2C, 1977CA02, 1977DE16, 1977JE04, 1977KI1K, 1977MO1Q, 1977NA13, 1977PO1A, 1977SA17, 1978BA31, 1978BI14, 1978DA1A, 1978HA1U, 1978KW1A, 1978LA1D, 1978LI1D, 1978MC04, 1978ON01, 1978OS01, 1978OS1B, 1978PO1A, 1978RO17, 1978SH04, 1978UL02, 1979CH06, 1979DA1K, 1979GA1D, 1979HE1F, 1979HE1G, 1979KI1C, 1979MA2F, 1979OS02, 1979QU1A).
Ground state of 12C: (1974DE1E, 1974EN10, 1975BE31, 1975CA1N, 1975FR05, 1975FR06, 1975KA29, 1975KU1N, 1975LE05, 1975LE1E, 1975MA50, 1975MU13, 1976BE1G, 1976FU06, 1976GA16, 1976GI11, 1976KI16, 1976SR1A, 1977AN21, 1977BE49, 1977FI12, 1977GR08, 1977JE04, 1977MA35, 1977MA1Y, 1977MY1A, 1977NO07, 1977PA25, 1977SA17, 1977TH03, 1978AN07, 1978BE56, 1978BI14, 1978GO1K, 1978HE1D, 1978MU04, 1978NA07, 1978NE03, 1978ON01, 1978RO17, 1978SM02, 1978SV01, 1978TA09, 1978UE1B, 1978UL02, 1978ZA1D, 1979GO1P, 1979PO03, 1979TA1K).
See also (1979BE1N) and reaction 44.
For E(6Li) = 1.2 to 2.8 MeV, population ratios of 7Be*(0.43), 7Li*(0.48) and 10B*(0.72) (reactions (e), (f) and (c)) remain approximately constant. Simple tunneling or compound nucleus models are not compatible with the data and a direct interaction through long-range tails is suggested (1962MC12). Absolute reaction cross sections at E(6Li) = 2.1 MeV are in reasonable agreement with estimates based on barrier penetration. A strong preference for α-emission suggests that the favored mechanism involves interacting clusters (1963HU02). The α0 yield shows a broad peak at E(6Li) ≈ 10 MeV (1970FR06: E(6Li) = 4 to 24 MeV). The yield of 6Li + 6Li → 3α (reaction (g)) for E(6Li) = 4 to 20 MeV is dominated by a broad resonance (Γ = 5 MeV) at the Coulomb barrier which is consistent with the formation of a quasimolecular state 6Li + 6Li with τ ≈ 10-21 sec (1970FR06). A multiparameter coincidence study of reaction (g) for E(6Li) = 2 to 13 MeV shows the importance of direct interactions: the data were fitted assuming an (α + d) cluster structure for 6Li and an interaction potential acting only between the two deuterons (1971GA21, 1972GA32). The cross section for reaction (g) rises rapidly for E(6Li) = 1.0 to 5.5 MeV. Thermonuclear reaction rates have been calculated for kT values of 10 to 1000 keV (1978NO1E). Cross sections for reaction (e) are reported at E(6Li) = 1.6, 3.5 and 5.0 MeV (1977RU06). See also (1975NO1C, 1976FI1F), 7Li, 7Be, 8Be and 10B in (1979AJ01), 11B and 11C here and (1975AJ02).
The elastic scattering (reaction (b)) follows the Mott formula at low energies [≲ 4.0 MeV] (1966PI02: E(6Li) = 3.2 to 7.0 MeV). A broad structure is observed in the excitation functions [θc.m. = 60° and 90°] at E(6Li) ≈ 13 MeV (1973GR34) and ≈ 26 MeV [Γ ≈ 7 MeV] (1971FO08: θc.m. = 90°; E(6Li) to 34 MeV). The elastic scattering appears to be dominated by absorption (1971FO08). Excitation functions for the transitions to 6Li*3.56 + 6Li*3.56 have been measured for E(6Li) = 28.0 to 33.0 MeV (1970NA02: θc.m. = 90°) and 28.0 to 36.0 MeV (1973WH02, 1974WH01, 1974WH02; θc.m. = 88°) [also ratio of 6Li*3.56 + 6Li*3.56 to formation of 6Heg.s. + 6Beg.s. at E(6Li) = 28, 32, 34 and 36 MeV]. The latter results have been compared with calculations using microscopic DWBA analysis. See also 6He and 6Li in (1979AJ01).
Excitation functions and angular distribution studies have been carried out by (1972BL17: E(3He) = 1.0 to 6.0 MeV; γ0, γ1, γ2), (1972LI29: 1.5 to 11 MeV; γ0, γ1, γ2, γ3), (1964BL12: 2 to 4.5 MeV; γ0, γ1) and (1974SH01: 3 to 21 MeV (γ2), to 24 MeV (γ0), to 26 MeV (γ1, γ3)). Observed resonances are shown in Table 12.9 (in PDF or PS).
12C*(28.2) appears to be formed by s- and d-wave capture. The γ0 and γ2 transitions to the 0+ states 12C*(0, 7.7) are strong and show a similar energy dependence. A strong non-resonant contribution is necessary to account for the γ1 yield (1972BL17). The resonance structure reported by (1974SH01) appears to confirm the role of 3p-3h configurations for 12C excitations somewhat above the giant resonance region. The γ3 yield is relatively unstructured (1972LI29, 1974SH01: to E(3He) = 26 MeV). See also (1975AJ02).
Excitation functions for neutrons [and production cross sections for 11C] have been measured for E(3He) = 1.2 to 10 MeV for several neutron groups: see (1968AJ02, 1975AJ02) for a listing of the earlier references. No sharp structure is observed but there is some suggestion from angular distribution data and excitation functions at forward angles for a broad structure (Γ ≈ 350 keV) at E(3He) ≈ 2 MeV: Ex = 27.8 MeV (1963DU12, 1965DI06). The total cross section for 11C production shows a broad maximum, σ = 113 mb at E(3He) = 4.3 MeV (1966HA21). Polarization measurements have been carried out for E(3He) = 2.1 to 3.9 MeV (1971TH15: n0, n1, n2+3: the shapes of the measured angular distributions for n0 and n1 show very gradual changes with energy. It is suggested that a significant direct interaction contribution is present (1971TH15). Excitation functions and angular distributions for protons (reaction (b)) have been measured for E(3He) = 1.0 to 10.2 MeV for a number of proton groups: see (1968AJ02, 1975AJ02) for a listing of the earlier references and (1977LI1F: 3 to 6 MeV). No pronounced structures are reported. Polarization measurements have been carried out at E(3He) = 14 MeV (1977IR01; P0, p1). For reaction (c) see (1974MO23; to E(3He) = 31 MeV). See also (1974LO1B) and 11B, 11C.
Analyzing powers have been measured at E(pol. 3He) = 33.3 MeV for nine proton groups (1976KA23). The cross section for ground state tritons (reaction (b)) increases monotonically for E(3He) = 2.5 to 4.2 MeV (1969OR01: θ = 40°) and then shows a broad maximum at E(3He) ≈ 4.5 MeV (1967EA01: θ = 20°). See also (1976UE01) for continuum measurements. See also (1974LO1B) and 9B, 10B in (1979AJ01).
The elastic scattering excitation function decreases monotonically for E(3He) = 4.0 to 9.0 MeV (1967EA01: θ = 45°) and 15.0 to 21.0 MeV (1972MC01: θc.m. = 90°). At θc.m. = 111° a slight rise is observed for E(3He) = 19 to 21 MeV (1972MC01). Polarization measurements have been reported at E(3He) = 18 (1972MC01), 31.4 (1971EN03) and 32.8 MeV (1975BU11; polarized 3He). See also (1976RO1L) and 9Be in (1979AJ01).
Excitation functions for the α0 group for E(3He) = 2 to 10 MeV show evidence of a complex structure at ≈ 4 MeV [Ex ≈ 29.3 MeV] (1978BI15: see also for σt and α0 in the range 2 → 10 MeV). Analyzing powers have been measured at E(pol. 3He) = 33.3 MeV for the groups to 8Be*(16.9, 17.6, 19.2) (1976KA23). See also (1974SA1K: 1.3 → 3.2 MeV) and (1976RO1L). Reaction (b) has been studied for E(3He) = 2.9 to 10 MeV (1975RO09, 1977GO16). See also (1979BA27), (1975AJ02) and 8Be in (1979AJ01).
Excitation functions measured for E(3He) = 4 to 10 MeV show some fluctuations: see (1975AJ02). See also 6Li in (1979AJ01).
Neutron groups have been observed to 12C*(0, 4.4, 7.7, 9.6, (10.1), (10.8)). Angular distributions of neutron groups have been measured at many energies in the range Eα = 1.75 to 23 MeV: see (1968AJ02, 1975AJ02) for references.
The mean life of 12C*(4.4) [Jπ = 2+] is 57+23-17 fsec, Γγ = 11.5+5-3.2 meV (1966WA10). 12C*(7.7) decays predominantly into 8Be + α: Jπ = 0+. See also Table 12.8 (in PDF or PS), (1978LO1C), (1974LO1B), (1978MC1F; applied work) and 13C in (1981AJ01).
At E(9Be) = 26 MeV, θlab = 10°, the population of 12C*(0, 4.4, 7.7, 9.6, 10.8, 11.8) is reported: the strongest transition is to 12C*(9.6) (1975VE10). See also (1975AJ02).
At E(9Be) = 26 MeV, θ = 10°, strong transitions are observed to 12C*(4.4, 7.7, 9.6) (1975VE10).
At E(3He) = 13 MeV neutron groups are observed to 12C*(0, 4.4, 7.7, 16.1, 17.8) and to excited states at Ex = 23.53 ± 0.04 [Γ < 0.4 MeV] and 27.611 ± 0.020 MeV. The latter is formed with a 0° cross section of ≈ 200 μb/sr and is taken to be the first 0+, T = 2 state of 12C (1974GO23).
The (d, γγ) excitation function [via the Jπ = 1+, T = 1 state at Ex = 15.1 MeV] has been measured for Ed = 2.655 to 2.91 MeV. The non-resonant yield of 15 MeV γ-rays is due to direct capture process or to a very broad resonance: no sharp resonances are observed corresponding to the T = 2 state reported in reaction 4 [Γd0Γγ/Γ ≲ 0.2 eV] (1970BL09, 1974HA1G). See also (1975AJ02).
The thin-target excitation function in the forward direction in the range Ed = 0.3 to 4.6 MeV shows some indication of a broad resonance near Ed = 0.9 MeV. Above Ed = 2.4 MeV, the cross section increases rapidly to 210 mb/sr at 3.8 MeV, and then remains constant to 4.6 MeV (1954BU06, 1955MA76). Excitation functions have also been measured for Ed = 3.2 to 9.0 MeV: see (1975AJ02). The branching ratios at 90° for the transitions to the ground states of 11C and 11B[n0/p0] have been measured for Ed = 1.0 to 2.0 MeV by (1973BR24).
Polarization measurements have been carried out for Ed = 1.20 to 4.0 MeV: see (1975AJ02). See also (1969WO09), (1974LO1B), (1977YO1F; applied) and 11C.
Yields of protons have been measured for Ed = 0.14 to 12 MeV: see (1968AJ02, 1975AJ02). No clear resonance structure is observed. There is some indication that a broad resonance, corresponding to 12C*(27.1) affects the p1 and p3 yields (1964BR1A). Upper limits for the partial widths (p0 → p3) of the T = 2 state reported in reaction 4 are given by (1970BL09).
Polarization studies have been carried out for Ed = 1.15 to 21 MeV: see (1968AJ02, 1975AJ02). See also 11B.
The yield of elastically scattered deuterons has been measured for Ed = 1.0 to 2.0 MeV: resonances at Ed = 1.0 and 1.9 MeV are suggested by (1969LO01). Excitation functions for the deuterons to 10B*(1.74, 2.16) [Jπ; T = 0+; 1 and 1+; 0, respectively] have been measured at several angles for Ed = 4.2 to 16 MeV: they are characterized by rather broad, slowly varying structures. The ratio σ1.74/σ2.15 varies from 0.69 ± 0.04% at Ed = 6.5 MeV to 0.16 ± 0.04% at Ed = 12.0 MeV corresponding, respectively, to isospin impurities of ≈ 2% and ≈ 0.5% (1974ST01). No resonance structure is observed in the elastic yield for Ed = 14.0 to 15.5 MeV (1974BU06). Polarization measurements are reported at Ed = 12.5 MeV (1975ZA08) and at 15 MeV (1974BU06). See also (1977IZ01; theor.) and 10B in (1979AJ01).
For polarization measurements at Ed = 15 MeV involving 9Be*(0, 2.43) and 9B*(0, 2.36) see (1974LU06). See also 9Be and 9B in (1979AJ01).
Excitation functions have been measured for the α0 and α1 groups for Ed = 0.4 to 12 MeV [see (1968AJ02, 1975AJ02)] and for Ed = 2.5 to 4.5 MeV (1975VA04; α0) and 0.8 to 9.0 MeV (1978BU04: α0). Maxima in the α0 yields are reported at Ed = 1, 2, 4.5 and (6) MeV. The first is attributed to an s-wave resonance corresponding to a state with Ex ≈ 26.0 MeV, Γ ≈ 0.5 MeV (1968FR07). The resonance structures at ≈ 2.0 and 4.5 MeV (Γ ≳ 1 MeV) may both involve the isoscalar giant resonance: Ex ≈ 28 MeV, Γ ≈ 4 MeV (1978BU04). No evidence for the T = 2 state was found in the α0 and α1 yield curves taken in 2 keV steps for 27.35 < Ex < 27.65 MeV (1970BL09). For yields of the α particles to 8Be*(17.6, 18.1) see (1970CA12) [also discussed in 8Be (1959AJ76)]. Reaction (b) has been studied for Ed = 2.7 to 5.0 MeV: see (1975RO09, 1975VA04, 1977GO16) and at Ed = 0.36 MeV (1977NO10). The latter work suggests that a 3- and a 4+ state in 12C contribute dominantly to the sequential decay. See also (1976GRZR) and (1979SE04; theor.).
See (1975AJ02) and 6Li in (1979AJ01).
Proton groups observed by (1958MO99, 1959AL96, 1962BR10) are displayed in Table 12.10 (in PDF or PS). Angular distributions of many of these groups have been measured for E(3He) = 1.4 to 14 MeV: see (1968AJ02).
From studies of 10B(3He, pα)8Be it is determined that 12C*(7.7, 9.6, 10.8, 14.1, 16.1) have natural parity π = (-1)J, and that 12C*(11.8, 12.7, 13.4), which decay only to 8Be*(2.9) and not to the ground state, have unnatural parity: see Tables 12.8 (in PDF or PS) and 12.10 (in PDF or PS) and (1968AJ02). 12C*(12.7) decays also by γ-emission. The charge dependent matrix element connecting 12C*(12.7, 15.1) is 110 ± 30 keV (1976AD03, 1977AD02): see also reactions 22, 44, 50, 73, 74 and 86. 12C*(16.11, 16.58) show decay to both 8Be*(0, 2.9). The consequent assignment of natural parity is consistent with Jπ = 2+ for the former but not with Jπ = 2- for the latter. For 12C*(16.11) observed values of Γα0/Γ are 0.05 - 0.12; the decay to 3α occurs rarely if at all (1966WA16). Table 12.8 (in PDF or PS) summarizes the decay parameters of some of the excited states of 12C.
Reactions (c) and (d) have been studied by (1970BO39). The latter, at E(3He) = 11 MeV, appears to proceed via a state in 12C at Ex = 20.5 ± 0.1 MeV, which is suggested to be Jπ = 3+, T = 1. The relative intensities of the decays of 12C states with 20 < Ex < 25 MeV via channels (c) and (d) is estimated. The α0 decay is very small, consistent with the expected population of T = 1 states (1970BO39). See also (1975NA1C), (1975MA21), (1976EP1A; astrophys.), 8Be in (1979AJ01) and 13N in (1981AJ01).
Angular distributions of d0 and d1 have been measured at Eα = 15.1 to 25.2 MeV (1975VA19). The relative populations of 12C*(12.71, 15.11) [both 1+; the latter isospin forbidden] leads to values of ≲ 260 keV (1975SP04), 285 ± 30 keV (1977LI02) for the charge dependent matrix element between these two states: see also reactions 21, 44, 50, 73, 74 and 86. See also (1976GU1B, 1976LE1K). (1978ZE03; theor.) and (1975AJ02).
At E(6Li) = 4.9 MeV angular distributions have been obtained for the α-particles to 12C*(0, 4.4, 7.7, 9.6). The population of 12C*(11.8, 12.7) is also reported (1966MC05), as is that of 12C*(15.11) [T = 1] (1964CA18: E(6Li) = 3.8 MeV): the intensity ratio α15.1/α12.7 = 3 ± 2%.
See (1975SE03, 1975SE04) and 11B.
Angular distributions involving 12C*4.4 + 12Cg.s. and 12C*4.4 + 12C*4.4 have been measured at E(14N) = 22.5 and 30 MeV (1969IS01) and 73.9 and 93.6 MeV (1977MO1A). See also (1973ST1A).
Angular distributions involving 14Ng.s. + 12Cg.s. and 14Ng.s. + 12C*4.4 have been measured at E(16O) = 30 and 32.5 MeV and also at 26 MeV for the double ground state transition (1969IS01).
In view of the complexity of the available information on these three reactions, we will first summarize the recent experimental results and then review the evidence for the parameters of 12C states observed as resonances.
(a) In the range 4 MeV < Ep < 14.5 MeV σ(γ0) is dominated by the giant dipole resonance at Ep = 7.2 MeV (Ex = 22.6 MeV, Γc.m. = 3.2 MeV), while the giant resonance in γ1 occurs at Ep ≈ 10.3 MeV (Ex = 25.4 MeV, Γc.m. ≈ 6.5 MeV): see (1964AL20). A study of the giant dipole resonance region with polarized protons (Ep = 6 to 14 MeV) sets new limits on the configuration mixing in the γ0 giant resonance (1972GL01). The E2 strength is found to be centered near Ep = 12 MeV: it exhausts ≳ 30% of the isoscalar E2 sum rule (1976MAZG, 1976MAZL). The analysis of γ1 is more complicated: the asymmetry results are consistent either with a single Jπ = 2- state or with interference of pairs of states such as (1-, 3-), (2-, 3-) and (1-, 2-) (1972GL01). See also (1979AR1G). Measurements of differential cross sections at 90° (Ep = 13 to 22 MeV), of angular distributions (Ep = 7 and 14 to 21 MeV), and of total cross sections (Ep = 14 to 21 MeV) have been reported by (1972BR26). The 90° yield of γ0, γ1, γ2 and γ3 [to 12C*(0, 4.4, 7.7, 9.6)] has been studied by (1977SN01): the γ2 yield shows a peak at Ep ≈ 14.3 MeV with a cross section ≈ 2.3% that of γ0 [in γ0 yield, Eres = 15.0 MeV (1977SN01), 14.8 MeV (1969KE02)] and perhaps as well a low intensity structure at Ep = 11.8 MeV. The γ3 yield exhibits two asymmetric peaks at Ep = 12.5 and 13.8 MeV (Γ ≈ 0.7 and 2.5 MeV) and a weaker structure at ≈ 9.8 MeV (1977SN01). The (pγγ) process [via 12C*(15.1)] has been studied in the vicinity of the first two T = 2 states; only a non-resonant yield is observed: (2J + 1)ΓγΓp/Γ < 0.25 eV and < 1.5 eV, respectively for 12C*(27.4, 28.6) (1977NA1F). At Ep = 40, 60 and 80 MeV, radiative capture is observed to a state, or a narrow group of states, at Ex = 19.2 ± 0.6 MeV (1979KO05). Work on other resonances is reported below.
(b) Excitation functions have been measured for Ep = 3.0 to 8.0 MeV (1975BO1H), 6.53 to 7.32 MeV (1977OH1A; α0, α1) and 6.0 to 18.0 MeV (1977BU07; α0). A wide resonance-like structure centered at Ep = 13 MeV [12C*(28)] with Γ ≈ 6 MeV is reported by (1977BU07): the angular distributions of α0 show prominent back peaking. See also (1978BU1D). Polarization measurements are reported for Ep = 2.62 to 2.66 MeV (1975MA49: α0).
(c) This reaction has been studied for Ep = 35.4 keV to 10.5 MeV. The total cross section has been measured for Ep = 35.4 to 1500 keV: it shows the 163 keV resonance and a broad peak centered at about 600 keV (σmax ≈ 0.9 b; read from Fig. 3). The 163 keV resonance has σR = 54 ± 6 mb and ΓRc.m. = 5.2+0.5-0.3 keV, Eres(c.m.) = 149.8 ± 0.2 keV [Ex = 16.1067 (5)]. The astrophysical S-factor and the reaction rate <σν> have been calculated. The values of <σν> obtained in this work suggest that the 11B(p, 3α) reaction may be a poorer candidate for CTR than previously thought (1979DA03). At higher energy the reaction proceeds predominantly by sequential two-body decays via 8Be*(0, 2.9): see in 8Be (1979AJ01), 12C [reaction 25] in (1975AJ02) and (1974KA1J, 1975KR1E, 1975VA04, 1977FU09, 1977GR10, 1977OH1A). Contributions from 12C*(23.0, 23.6, 25.4) are also reported (1975VA04).
See also (1976BO08, 1977AV01: spallation), (1977MC1C, 1977TR1E, 1978ZI1A: applications), (1974LO1B, 1976GL1E, 1979BL1J, 1979SN1A) and (1976GA1K, 1977GA1H, 1978GA13, 1979RAZW; theor.).
The parameters of the observed resonances are displayed in Table 12.11 (in PDF or PS). The following summarizes the information on the low-lying resonances: for a full list of references see (1968AJ02).
Ep = 0.16 MeV: [12C*(16.11)]. This is the Jπ = 2+; T = 1 analog of the first excited states of 12B and 12N. The γ-decay is to 12C*(0, 4.4, 9.6), and also 12C*(12.71) [see Table 12.8 (in PDF or PS)]: the angular distribution of γ3, together with the known α-decay of 12C*(9.6), fix Jπ = 3- for the latter (1961CA13). A new measurement of the (p, γ) and (p, α) resonant cross sections yields 125 ± 16 μb and 38.5 ± 3.2 mb, respectively, based on Γc.m. = 6.7 keV. Γγ and Γp for 12C*(16.11) are then 21.7 ± 3.3 eV and 21.7 ± 1.8 eV, respectively (1974AN19). (1977AD02) report Γγ0 = 0.75, Γγ1 = 16.2, and Γγ7 = 0.24 eV: see, however, Table 12.8 (in PDF or PS).
Ep = 0.67 MeV: [12C*(16.58)]. The proton width [Γp ≈ 150 keV] indicates s-wave protons and therefore Jπ = 1- or 2-. This is supported by the near isotropy of the two resonant exit channels, α1 and γ1. The α1 cross section indicates 2J + 1 ≥ 5: therefore Jπ = 2-. [This is consistent with the results of an α - α correlation study via 8Be*(2.9) (1972TR07).] The γ1 E1 transition has |M|2 ≈ 0.1 W.u., suggesting T = 1 (1957DE11, 1965SE06).
Ep = 1.4 MeV: [12C*(17.23)]. (2J + 1)Γγ0 ≥ 115 eV. This indicates Jπ = 1-, with T = 1 most probable (1965SE06). Jπ = 1- is also required to account for the interference at lower energies in α0 and γ0 [see (1957DE11)] and is consistent with the α - α correlation results of (1972TR07). Two solutions for Γp are possible; the larger (chosen for Table 12.11 (in PDF or PS)) is favored by elastic scattering data (1965SE06). See, however, (1975KR1E).
Ep = 2.0 MeV: [12C*(17.8)]. The resonance in the yield of α0 requires natural parity, the small α-widths suggest T = 1. For Jπ = 1- or 3- the small γ-widths would be surprising; Jπ = 2+ would lead to a larger anomaly than is observed. Jπ is then 0+, T = 1 (1965SE06).
Ep = 2.37 MeV: [12C*(18.13)]. Seen as a resonance in the yield of 15.1 MeV γ-rays: σR = 0.77 ± 0.15 μb, Γc.m. = 600 ± 100 keV, (2J + 1)Γγ ≥ 2.8 ± 0.6 eV. The results are consistent with Jπ = 1+, T = 0, but interference with a non-resonant background excludes a definite assignment (1972SU08).
Ep = 2.62 MeV: [12C*(18.35)]. The resonance for α0 requires natural parity; the presence of a large P4 term in the angular distribution requires J ≥ 2 and lp ≥ 2. The assignment Jπ = 3- is consistent with the data (1965SE06, 1972CH35, 1972VO01, 1974GO21).
Ep = 2.66 MeV: [12C*(18.40)] is not seen here: see 11B(p, p).
Ep = 3.12 MeV: [12C*(18.80)]. The angular distribution of γ0 indicates E2 radiation, Jπ = 2+. This assignment is supported by the angular correlation in the cascade γ1 and by the behavior of σ(α0); T = 1 is suggested by the small Γα (1965SE06).
The structure near Ep = 3.5 - 3.7 MeV [12C*(19.2, 19.4)] seems to require at least two levels. The large Γγ0 requires that one be Jπ = 1-, T = 1 and interference terms in σ(α0) require the other to have even spin and even parity: Jπ = 2+; T = 0 is favored (1963SY01, 1965SE06). Resonances at Ep = 4.93 and 5.11 MeV, seen in σ(γ1) (1955BA22) also appear in σ(α1), but not in σ(α0). Angular distributions suggest Jπ = 2+ or 3- for the latter [12C*(20.64)]; the strength of γ1 and absence of γ0 favors Jπ = 3-, T = 1 (1963SY01).
The first seven T = 1 states in 12B and 12C have been identified by comparing reduced proton widths obtained for this reaction and reduced widths obtained from the (d, p) and (d, n) reactions: see Table 12.12 (in PDF or PS) (1971MO14, 1974AN19). See also (1977AD02).
Excitation functions have been reported for Ep = 2.6 to 11.5 MeV. They are characterized by numerous peaks: see Table 12.13 (in PDF or PS). The positions of these appear to correspond with 11B(p, α)8Be and with some of the (γ, n) and (γ, p) structure, suggesting that resonances, and not fluctuations, are involved. Angular distributions do not change as rapidly as might be expected from the pronounced structure in the excitation function (1965OV01).
Polarization transfer coefficients for n0-bar have been measured for Ep-bar = 7.3 to 14.8 MeV (1976LI08) and 16.3, 21.3 and 26.5 MeV (1976HI11). The lower energy work shows a strong peak at Ep-bar = 9 MeV (1976LI08). (1976HI11) find that the results are not in agreement with direct reaction theory calculations using a charge-exchange effective interaction which includes both central and tensor forces. See also (1974MA07; theor.) and (1975AJ02). See also 11C, (1977ME1C), (1977YO1G, 1979OV1A; applications), (1976WA1B) and (1977GA1H, 1978DE37; theor.).
Anomalies and maxima observed in the excitation functions of p0 and p1 are displayed in Table 12.13 (in PDF or PS). Recent studies are reported at Ep = 1.8 to 3.1 MeV (1975MA49, 1976MA64; p0), Ep-bar = 1.9 to 3.0 MeV (1977MA37; p0), Ep = 3.0 to 5.2 MeV (1977RI01; p0), 3 to 8 MeV (1975BO1H: prelim.; p0 → p3), 7.5 to 10.5 MeV (1975VA04; p0, p1) and 19.2 to 47.4 MeV (1978NA03; σt).
Polarization measurements have been carried out at a number of energies for Ep = 1.9 to 155 MeV: see (1975AJ02). (1977MO09) have observed polarization transfer in order to study the spin-flip process at Ep-bar = 32 MeV: the cross section is lower than that predicted by DWBA. See also (1975MA1H, 1976PH01, 1977PH02; theor.). For reactions (c) and (d) see 10Be, 10B in (1979AJ01).
Reported neutron groups are displayed in Table 12.14 (in PDF or PS). Angular distributions have been studied in the range 0.5 < Ed < 11.8 MeV: see (1968AJ02, 1975AJ02) for a listing of the references. See (1971MU18) for a discussion of the problems involved in comparing spectroscopic factors obtained in this reaction and in the (3He, d) reaction [reaction 31]. Angular correlation studies involving 12C*(4.4, 15.1) have been carried out at many energies in the range 0.7 < Ed < 6.3 MeV.
In the range Ed = 1.0 to 5.5 MeV, two slow neutron thresholds are observed at 1.627 ± 0.004 MeV (Ex = 15.109 ± 0.005 MeV) and near 4.1 MeV (broad; Ex = 17.2 MeV) (1955MA76). At the lower threshold, 15.1 MeV γ-rays are observed: Ed = 1.633 ± 0.003 MeV, Γ < 2 keV (1958KA31) [Ex = 15.110 ± 0.003 MeV].
A study of the angular distributions and energy spectra of α-particles from the decay of 12C states shows that the 12.71 and 11.83 MeV states decay sequentially via 8Be; the former via 8Be*(2.9), the latter 90% via 8Be*(2.9) and 10% via 8Be(0). There is some evidence that the 10.84 MeV state decays primarily to 8Be(0). Jπ = 3- for the 9.64 MeV state is favored on the basis of the angular distribution of the α-particles to 8Be(0). There is no evidence for direct 3α decay of 12C levels in the range Ex = 9 to 13 MeV, nor does 12C*(10.3) appear to participate in this reaction (1965OL01). See also (1978GR07) and 13C in (1981AJ01).
Observed deuteron groups are displayed in Table 12.14 (in PDF or PS). Angular distributions have been measured at E(3He) = 5.1 to 44 MeV [see (1975AJ02)] and at E(3He) = 23.2 MeV (1977KA1R: d to 12C*(12.71, 15.11)). 13N*(15.1) [T = 3/2] has been observed to decay to 12C*(9.6, 10.8) with branching ratios of (9.6 ± 1.4)% and (16.4 ± 3.6)% respectively (1979AD01). See also 13N in (1981AJ01).
Angular distributions have been measured at five energies in the range Eα = 15.1 to 46 MeV [see (1975AJ02)], at Eα = 25.1 MeV (1974DM01: t0, t1) and at 120 MeV (1979CHZP). The (t1, γ) angular correlations have been measured for Eα = 21.2 to 25.0 MeV (1972EL09). See also (1976GU1B, 1976LE1K) and (1978ZE03; theor.).
Angular distributions have been measured for the ground state transition at E(14N) = 41, 77 and 113 MeV: they show damping of the oscillations with increasing energy (1971LI11).
Angular distributions have been measured at E(16O) = 27, 30, 32.5, 35 and 60 MeV for the transitions 15Ng.s. + 12Cg.s., 15N*6.3 + 12Cg.s., 15Ng.s. + 12C*4.4 and 15Ng.s. + 12C*9.6 (the latter at E = 60 MeV only) (1972SC03): at the highest energy the ratio θ2/θ2g.s. for the transition 11Bg.s. + p → 12C is 0.12 and 0.05, respectively for 12C*(4.4, 9.6). See also (1975SC35) and (1974FL1A, 1975OS01, 1976DE08, 1977GO1D, 1977WE1H; theor.).
The decay is mainly to 12Cg.s.; branching ratios to 12C*(0, 4.4, 7.7, 10.3) are displayed in Table 12.15 (in PDF or PS). All the observed transitions are allowed. The half-life is 20.20 ± 0.02 msec (1978AL01). See also Table 12.2 (in PDF or PS) of (1968AJ02).
12C*(7.7) is of particular interest for helium burning processes in stars [see (1968AJ02)]. The fact that the β-decay is allowed indicates Jπ = 0+, 1+ or 2+; it decays primarily by α-emission eliminating Jπ = 1+, and requiring 0+. (1973BA73) have measured the Q of the α-decay of 12C*(7.7) to be 379.6 ± 2.0 keV. When this result is combined with the Q determined from accurate measurements of the Ex of 12C*(7.7), the "best" value is Q = 380.1 ± 1.1 keV. This value, together with previously measured values of Γπ, Γπ/Γ and Γrad/Γ lead to Γrad = 3.41 ± 1.12 meV and to a mean lifetime for the destruction of helium by the [ααα] process of 2.59 x 10-8ρ2T-39exp(-4.411/T9) sec-1 (1973BA73). See, however, Table 12.8 (in PDF or PS). A search for transitions to 12C*(12.7) has been unsuccessful (1967AL03).
(1978LE02) have measured the alignment correlation term which leads to α-(E0) = -(1 ± 2)%/MeV; (1978BR01) find α- = +(0.24 ± 0.44)%/MeV. The shapes of the β-spectra of 12B and 12N have both been analyzed [see reaction 69]. The values for α- - α+ are all now in agreement with the predictions of CVC and with the absence of second class currents: see, e.g., (1977KA24, 1977SU1F, 1977WU01, 1978MO02, 1979KO12).
See also (1975MI1F, 1975ST1H, 1975SU01, 1976SU1C), (1973MIYZ, 1974AD1B, 1976BE1E, 1977GA1E, 1977RI08, 1977TE1B, 1978CA1H, 1978WE1J, 1979DO1A) and (1975BE24, 1975DO10, 1975DO1D, 1975IM02, 1975KU20, 1975MO1F, 1975RH1A, 1975WI1E, 1976CA29, 1976KH05, 1976MO1G, 1976SU09, 1976YO1D, 1977AZ02, 1977BE2A, 1977CA1M, 1977HW01, 1977KU1E, 1977MA2D, 1977OK1A, 1977WA1F, 1977YA1D, 1977YO1D, 1978BE1V, 1978BE58, 1978KU1A, 1978MO02, 1978PA06, 1978SE1B, 1978SZ07, 1979DE15, 1979PR1D, 1979SZ02; theor.).
Resonance scattering and absorption by 12C*(15.11) have been studied by many groups: see Table 12.15 (in PDF or PS) in (1968AJ02) and (1970AH02, 1976ME25). The partial widths are displayed in Table 12.8 (in PDF or PS). Elastic scattering to 12C*(4.4, 16.1, 17.2) has also been observed. The Ex of 12C*(4.4) is 4439.4 ± 1.6 keV (1977WE1C). Rayleigh scattering has been studied at θ = 1.02° for Eγ = 0.4 to 3 MeV by (1978KA1P) and nuclear Thomson scattering for Eγ = 5.5 to 7.2 MeV (1977BE32: θ = 140°). At higher energies elastic scattering studies show the giant resonance peak at ≈ 24 MeV. A considerable tail is visible, extending to > 40 MeV (1959PE32). See also (1975RO1N, 1976VE06, 1977CR1C, 1977HA1W, 1979KA1Q), (1975BR1F), (1975AJ02) and reaction 38.
The total absorption, mainly (γ, n) + (γ, p), is dominated by the giant resonance peak at 23.2 MeV, Γ = 3.2 MeV [σmax = 21 mb (1975AH06)] and by a smaller structure at 25.6 MeV, Γ ≈ 2 MeV [σmax ≈ 13 mb (1975AH06)]: see (1968AJ02, 1975AJ02) for a detailed listing of the earlier references and results. The attenuation coefficient of 6.42 MeV γ-rays has been measured by (1975MO27).
The (γ, n) cross section shows a giant resonance centered at about 22.5 MeV, Γ ≈ 3 MeV (σmax ≈ 8 mb), a secondary maximum at 25.5 MeV, Γ ≈ 2 MeV, and a long tail: see (1966FU02, 1966LO04, 1975KN10), (1975BE1F, 1976BE1H) and (1968AJ02). The (γ, n0) cross section has been measured at 90° for 21 < Ex < 40 MeV and compared with the (γ, p0) cross section (1968WU01): the isospin mixing averages about 2% in intensity and shows structure at the giant resonance. Angular distributions of n0 measured over the giant resonance region indicate that the main excitation mechanism is of a 1p3/2 → 1d5/2 E1 single particle character. No significant E2 strength is observed (1968RA21). See also (1975AJ02), 11C and (1975SC05). The production cross section of 11C by 30 MeV electrons is 11.92 ± 0.15 μb: this corresponds to an electric dipole (γ, n) integrated cross section to 30 MeV of 41.0 ± 0.6 MeV · mb (1978KL03). Pair production by 6.6 MeV γ-rays in carbon has been studied by (1976RO1N).
The cross section for reaction (b) has been measured for Eγ = 35 to 130 MeV. The (γ, 2n) cross section is very much smaller than that for (γ, n): the highest value is 0.15% of the maximum value for reaction (a) in the energy range Eγ = 20 to 140 MeV (1970KA37). The 10C production cross section has been measured for Ebs = 100 to 800 MeV (1977JO02). See also (1975NO10, 1975WO04, 1977BA3D, 1977HI12), (1974BU1A, 1975BE60, 1977DA1B, 1979BO1U), (1976WA1J; applications) and (1975WO07, 1976HE12, 1977GR08, 1977WU02, 1978KA1Q; theor.).
The photoproton cross section exhibits two broad peaks, the giant resonance peak at 22.5 MeV, Γ = 3.2 MeV, σmax = 13.1 ± 0.8 mb and a 2 MeV broad peak at 25.2 MeV, σmax = 5.6 ± 0.3 mb: see (1976CA21) and Table 12.19 (in PDF or PS) in (1968AJ02). While the E1 component dominates in the GDR, a 2% E2 contribution may possibly be present (1976CA21). In contrast with the giant resonance peak in the (γ, n) cross section, the (γ, p) cross section shows a strong peak in the center of the broad giant resonance peak. Above 24.5 MeV the ground state (γ, p) and (γ, n) excitation functions have the same shape up to at least 36 MeV (E.G. Fuller, private communication). There is agreement between the (γ, p) results and those from the inverse reaction 11B(p, γ0)12C [see reaction 27] when the population of 11B*(4.4, 5.0) is taken into account. See also (1975AJ02). The fraction of transitions to the ground and excited states of 11B have been determined at several energies in the range Ebs = 24.5 to 42 MeV: most of the transitions are to 11Bg.s. and the excited state transitions appear to originate from localized Ex regions (1970ME17). The cross sections for (γ, p0) and (γ, p0 + p1) have been measured at Eγ = 60, 80 and 100 MeV (1976MA34). See also 11B and (1978KI03).
(1978BA50) have studied the momentum distribution of π+ and π- for Eγ = 300 to 850 MeV and (1978AR08) have measured the cross section for π- production in the range 510 to 750 MeV. The cross section for π+ production, summed over 12B states, has been measured for Ebs to 175 MeV (1979MI06). See also the "Pion capture and pion reactions" section here, (1976BE39, 1979BOZW, 1979PA06, 1979SH1N) and (1975AJ02). See also (1975TO10, 1976KU1C, 1977AL33, 1977AL1P, 1977KI1J, 1979AL1T), (1976GA02) and (1975AN1H, 1975BI05, 1975FU07, 1976HE12, 1977FI12, 1977NE2A, 1978FI10, 1978FU09, 1978WO11; theor.).
Cross sections and angular distributions of the deuterons corresponding to transitions to 10Bg.s. and/or low excited states have been measured at Eγ ≈ 40 MeV: the results are consistent with E2. There is some evidence also for the excitation of higher states of 10B via non-E2 transitions (1972SK08). For Ebs = 90 MeV, the ratio of yields of deuterons to protons is ≈ 2%, for particle energies 15 to 30 MeV. For higher particle energies, the ratio decreases (1962CH26). For reaction (b) see (1975AJ02).
The yield of tritons has been measured for Eγ = 35 to 50 MeV by (1967KR05). For reaction (b) see (1969TA11).
The cross section exhibits broad peaks at about 18 MeV and ≈ 29 MeV; a pronounced minimum occurs at 20.5 MeV: to what extent the peaks have fine structure is not clear: see (1964TO1A) and (1968AJ02). For Eγ < 22 MeV, transitions are mainly to 8Beg.s. and 8Be*(2.9) with the g.s. transition dominating for Eγ ≲ 14 MeV. For Eγ > 26.4 MeV, 8Be (T = 1) levels near 17 MeV are strongly excited (1955GO59). Alpha energy distributions show surprisingly strong E1 contributions below Eγ ≈ 17 MeV (1955GO59, 1964TO1A). See also (1976TU05, 1979FL1G) and (1978DZ01, 1978MY1B; theor.).
The yield of 0.48 MeV γ-rays from the decay of 7Be, formed in reaction (b), shows a resonance at Eγ ≈ 29.5 MeV, σ = 0.9 ± 0.2 mb (1969OW01). For work on the γ-induced spallation of 12C see (1968AJ02, 1975AJ02) and (1976TU05).
The nuclear charge radius of 12C, Rrms = 2.472 ± 0.002 fm (1979CA1G). Other values include Rrms = 2.445 ± 0.015 fm (Fermi model), 2.453 ± 0.008 fm (shell model) (1972JA10), 2.462 ± 0.022 fm (1973FE13), 2.45 ± 0.04 fm (1979DO1M). See also (1975AJ02). Elastic scattering has been studied up to 4 GeV: see (1968AJ02, 1975AJ02).
12C states observed in inelastic scattering are displayed in Table 12.16 (in PDF or PS). The variation of the form factor F(q2) with momentum transfer yields unambiguous assignments of Jπ = 2+, 0+ and 3- for 12C*(4.4, 7.7, 9.6): see (1975AJ02) and (1978CR1A, 1979CR1D, 1979FL1F). The isospin mixing between the 1+ states 12C*(12.7, 15.1) has been measured by (1974CE01): β = 0.19 ± 0.01 or 0.05 ± 0.01. See also reactions 21, 22, 50, 73, 74 and 86. A study at Ee = 57 to 215 MeV (θ = 180°) of the transverse form factors squared of the 2+ states 12C*(4.4, 16.1) indicates appreciable contributions of nuclear convection currents to the T = 0 state at low momentum transfer and spin magnetization contributions to the T = 1 state at higher q (1978FL09). Longitudinal and transverse form factors of 12C*(16.1) have been studied by (1978FR03) at Ee = 32.8 to 62.2 MeV. The ground state branching ratio for 12C*(17.76) is < 10-9 (1979CR1D).
Inelastic scattering of the giant resonance has been studied by many groups: see (1968AJ02) and Table 12.16 (in PDF or PS). The longitudinal form factors show 12C*(16.1, 18.6, 20.0, 21.6, 22.0, 23.8, 25.5) while the transverse form factors show 12C*(15.1, 16.1, 16.6, 18.1, 19.3, 19.6, 20.6, 22.7, (25.5)) (1970AN1C, 1970TO13, 1971YA03, 1972AN03). 12C*(19.3) may be the expected giant magnetic quadrupole state, Jπ = 2-: see (1975AJ02). See also (1978FA1F, 1979FL1F).
See also (1975BE1T, 1975LA23, 1975LU1B, 1976BU1H, 1976VL01, 1977HA1W, 1978DE32, 1979FLZZ), (1974DE1E, 1975FA1A, 1975HU1D, 1977RI1H, 1979LI06, 1979BE2E) and (1974UBZY, 1974WA1C, 1975AB1E, 1975BE12, 1975BO27, 1975DO10, 1975DO1D, 1975FR05, 1975IN04, 1975KI21, 1975LA1G, 1975LE14, 1975OK1A, 1975WA30, 1975WE1A, 1976BU1B, 1976BU1G, 1976BH1B, 1976GU11, 1976KA07, 1976RA28, 1976TA1F, 1977AG03, 1977AH04, 1977BR37, 1977DE16, 1977FU1M, 1977FU1E, 1977GR02, 1977GR24, 1977GU1D, 1977RI1H, 1977VI03, 1977WA1F, 1977WA1G, 1978AL04, 1978BU1K, 1978DO1D, 1978DU12, 1978FU13, 1978GU13, 1978HO1E, 1978KO32, 1978MA1U, 1978MU04, 1978RI1C, 1978SE1B, 1978UE1B, 1979AM02, 1979CA1H, 1979FR1C, 1979GO1Q, 1979IN06, 1979KA1P, 1979KN1E, 1979PEZX, 1979PO03, 1979SA20, 1979SE06; theor.).
Electron spectra in the region of large energy loss show a broad peak which is ascribed to quasi-elastic processes involving ejection of single nucleons from bound shells: see (1968AJ02). Studies of e' - p coincidences for Ee = 497 to 700 MeV reveal peaks corresponding to ejection of 1p and 1s protons: the energy of the two peaks [Γ = 6.9 ± 0.1 and 19.8 ± 0.5 MeV] are 15.5 ± 0.1 and 36.9 ± 0.3 MeV (1976NA17: 700 MeV; DWIA). By studying the missing energy spectrum at Ee = 497 MeV (1976MO17) the population of 11B*(2.14, 5.0) [as well as of 11Bg.s. (1974BE12)] is reported. See also (1975AJ02) and (1977ZI1B). The deep inelastic response function has been studied by (1978MO19: Ee = 160 to 520 MeV, θ = 60° and 130°): a pronounced transverse strength is found in the region between the quasielastic and the N peaks.
For reaction (b) see (1975WO04) and (1975AJ02). For reaction (c) see (1977SH14) and 12B. For reaction (d) see (1976HE13). For both see also the "Pion capture and pion reactions" section here.
See also (1977KN04, 1979FI1D, 1979FR1B, 1979PA1G, 1979PA1K, 1979SC1E, 1979SH1N, 1979ZI1D) and (1974JA1N, 1975AN1K, 1975DI1G, 1975DZ04, 1975GO33, 1975KA40, 1975RO18, 1975WO07, 1976BE60, 1976GO08, 1976NA03, 1976TA1G, 1977BE67, 1977FI12, 1977HA23, 1977KA1T, 1977MC1F, 1977NE2A, 1978FU04, 1978HA36, 1978KE1F, 1978NA20, 1978TA1D, 1979BE2F, 1979BO07, 1979FIZW, 1979KL1C; theor.).
Angular distributions of the scattering (primarily elastic at forward angles) have been measured at Eπ = 29 MeV (1978JO09; π-), 29.2 and 49.5 MeV (1979GY1B; π-), 50 MeV (1977DY02, 1978MO25, 1979DY02; π+), 120 to 280 MeV (1970BI1A; π-), 125 MeV (1979NA04; π+), 162 MeV (1978MO23; π+) and 150, 162, 226 MeV (1977PI02, 1977PI09, 1979CH05; π+ and π-). Inelastic distributions to 12C*(4.4, 9.6) are reported by (1977DY02; Eπ+ = 50 MeV), (1970BI1A; Eπ- = 120 to 280 MeV; also to 12C*(15.0)), (1979CH05; also to 7.7; Eπ+ = Eπ- = 162 MeV), (1978TH1C; Eπ- = 162 MeV) and (1978MO23; Eπ+ = 162 MeV; also to 19.3). Observation of 4.4 MeV γ-rays at Eπ = 73 MeV leads to a cross section ratio (π-/π+) of 1.23 ± 0.22. The cross section is 14.5 ± 3.0 mb for π+ (1970HI10). At Eπ+ = 148 MeV, 12C*(7.6, 15.1) are also populated (1978PE11). See also (1977GR1G, 1979MOZW). (Comparison of π+ and π- inelastic scattering at Eπ = 180 MeV shows structures at Ex ≈ 19.2 - 19.7 MeV which may be due in part to an isospin-mixed 4- doublet (1979CO1N). Angular distributions have been reported at Eπ+ = 100 to 300 MeV for 12C*(4.4, 7.7, 9.6, 19.3) (1979AL1U). Preliminary values for the isospin mixing of 12C*(12.71, 15.11) and 12C*(18.4, 19.4) are 125 ± 35 and 250 ± 50 keV, respectively (1979BO2D, 1979MO1W; prelim.; Eπ = 116, 180 MeV). See also (1979CO1L).) The absorption cross section at Eπ+ = 125 MeV is 161 ± 28 mb (1979NA04). The emission of 2 photons in the capture of stopped pions, i.e. (π-, γγ), occurs at a rate of ≈ (1.3 ± 0.3) x 10-5/capture (1979DE06). See also (1977RO21, 1979MA2J). For the (π+, π+p) reaction see (1978CO02). For reaction (c) see (1973AS1A). See also the "Pion capture and pion reactions" section here.
Elastic and inelastic scattering to 12C*(4.4, 7.7, 9.6, 10.3, 10.8, 11.8) have been studied at many energies up to 350 MeV: see (1968AJ02) and Table 12.19 (in PDF or PS) in (1975AJ02). Recent angular distribution measurements have been reported at En = 1.5 to 4.0 MeV (1975HO1G, 1978SM1D; n0, natural C), 8.0 to 14.5 MeV (1978HA1P; n0, n1), 8.97 to 14.93 MeV (1976GL11; n0, n1), 14.2 MeV (1978ME12; n0, n1), 14.2 MeV (1978DR03; n1γ) and 14.6 MeV (1975KO27; n0). Angular correlations (n1, γ4.4) have been studied at En = 13.9 to 15 MeV: see (1975AJ02). For a brief discussion of studies of the spin-flip probability for the transition to 12C*(4.4) see (1975AJ02). See also 13C in (1976AJ04, 1981AJ01).
At En = 14.4 MeV reaction (b) involves 12C*(9.6, 10.8, 11.8, 12.7): see (1975AJ02, 1976CO1N). For reaction (c) see (1978RI02). See also (1975AN1J, 1975AN1G, 1975HO1F, 1975JE01, 1975PO08, 1976HA1N, 1977WHZZ), (1976MC1E, 1976WA1B, 1978FU1G) and (1976CA13, 1976TH10, 1977NO07, 1978AD1A; theor.).
Angular distributions of elastically and inelastically scattered protons have been measured at many energies up to Ep = 1040 MeV: see Tables 12.22 (in PDF or PS) in (1968AJ02), 12.20 (in PDF or PS) in (1975AJ02) and 12.17 (in PDF or PS) here.
Table 12.18 (in PDF or PS) displays the information on excited states of 12C. The newly reported value of Ex = 7654.00 ± 0.20 keV leads to a Q-value for the decay of this state into 3α of 379.31 ± 0.21 keV (1976NO02) and J. Nolen, private communication): this implies an increase of 9%, at a stellar temperature of 108° K, in the 3α reaction rate calculated by (1975FO19). A summary of the information on the decays of this and other excited states of 12C is shown in Table 12.8 (in PDF or PS).
The spin-flip probability (SFP) for the transition to 12C*(4.4) has been measured for Ep = 15.9 to 37.6 MeV: two bumps appear at ≈ 20 and ≈ 29 MeV. It is suggested that the lower one is due to a substructure of the E1 giant dipole resonance while the upper one results from the E2 giant quadrupole resonance (1975DE32). See also the studies listed in (1975AJ02). SFP has also been measured for 12C*(12.71) at Ep = 42 MeV (1977MO18) and for 12C*(12.7, 15.1) for Ep = 23.5 to 27 MeV (1978HOZJ). The relative population of 12C*(12.7, 15.1) has been measured at Ep = 800 MeV, θ = 5.8°: it is roughly 1 : 2 (1978BO1Q).
The angular distributions of the proton groups to 12C*(4.4, 12.7, 15.1) for Ep = 22.5 to 45 MeV have been analyzed by (1975GE15) to obtain the structures of the giant resonances. It is suggested that the E2 strength is fragmented, with the major concentration, corresponding to the isoscalar E2 resonance, near 28 MeV, and subsidiary strength near 32 and 42 MeV, the latter possibly a part of the isovector quadrupole resonance. See also the structures reported by (1977BU19) and displayed in Table 12.18 (in PDF or PS).
For polarization measurements see 13N in (1976AJ04, 1981AJ01). See also (1975KA2D, 1976FR05, 1977BR33, 1977DY1C, 1977SP1D, 1979BLZY, 1979BU1D), (1975IG1A, 1976SL2A, 1977AL1U, 1977SP1B, 1978AL1G, 1978ER1C,1978IG1B, 1979LI06), (1976CR1D; astrophys.), (1978GO1E; applied) and (1974SA1G, 1974SC1E, 1975AH1C, 1975AH03, 1975AH1E, 1975BR14, 1975CL1D, 1975DU1A, 1975FR13, 1975GU11, 1975MA23, 1975NA07, 1975SC1T, 1975ST1M, 1975VI09, 1976AB05, 1976BU01, 1976HO1E, 1976KO1G, 1977AH04, 1977AL15, 1977AL19, 1977GU1D, 1977GU1E, 1977KH02, 1977KO1T, 1977NE06, 1977PH02, 1977SU1E, 1977VI03, 1977WE1K, 1978BE64, 1978BE1Y, 1978BE66, 1978CO1J, 1978FA04, 1978GU12, 1978KO32, 1978LE06, 1978MA34, 1978RA20, 1979AB01, 1979AM02, 1979BO03, 1979DY1E, 1979JA1L, 1979PEZX; theor.).
The (p, 2p) reaction has been studied at energies up to 1 GeV: see (1975AJ02) for the earlier work, 11B and (1976BH02, 1977KO08, 1977NA16, 1977NA29, 1978KO30). See also (1978CH1K, 1979KRZX). For reaction (b) see (1975AJ02), (1976HO19) and 13N in (1981AJ01). For reaction (c) see 10B in (1979AJ01), (1977GR04) and 13N in (1981AJ01). See also (1978AZ1B). For reactions (d, e) see (1976GR1H, 1977GR04).
At Ep = 56.5 MeV reaction (f) proceeds primarily by sequential α-decay: initially 12C*(19.7 ± 0.5, 21.1 ± 0.3, 22.2 ± 0.5, 26.3 ± 0.5) are formed. These states, which must therefore have natural parity and a significant T = 0 admixture, subsequently decay to 8Beg.s. [12C*(22.2, 26.0)] or 8Be*(2.9) [12C*(19.7, 21.1, 26.3)] (1969EP01). At Ep = 100 MeV reactions (f) and (g) to 8Beg.s. have been studied by (1977CO07, 1977RO02): <Sα> = 0.59 ± 0.05 and 0.56 ± 0.12, respectively. For reaction (f) see also 8Be and (1978CH1H, 1978DE1J, 1978LA11). For pion production see (1978PE12).
See also (1977BA85, 1977WA05, 1978AZ02), (1975RO1B, 1977MC1F, 1977RO1E, 1975SC1V, 1978CH1C) and (1974JA1N, 1975BA1H, 1975EI1B, 1975FR06, 1975SA01, 1976BI11, 1976KO08, 1976LE02, 1977JA1F, 1977KO1P, 1978BA1C, 1978GO1L, 1978HA35, 1978TA1H, 1978WO1A, 1978WR01, 1979CH06, 1979FA1B, 1979FU1J, 1979GU1F, 1979LA02, 1979MA20; theor.).
The angular distribution of elastically and inelastically scattered deuterons has been studied at many energies up to Ed = 650 MeV: see (1968AJ02), Table 12.22 (in PDF or PS) in (1975AJ02) and Table 12.17 (in PDF or PS) here. Ex of 12C*(4.4) is 4440.5 ± 1.1 keV (1974JO14). The isospin mixing of 12C*(12.7, 15.1) [Jπ = 1+; T = 0 and T = 1] gives a mean charge dependent matrix element of 324 ± 33 keV (1977LI02: Ed = 24.1 to 28.8 MeV). See also (1976COYZ), (1975AJ02) and reactions 21, 22, 44, 73, 74 and 86. The quadrupole deformation parameter is calculated to be β2 = -0.48 ± 0.02 independent of incident energy [Ed = 60.6, 77.3, 90.0 MeV] (1975AS06; coupled channels analysis). (1971DU09) report β2 = 0.47 ± 0.05 and β3 = 0.35 ± 0.06 for 12C*(4.4, 9.6) [Ed = 80 MeV].
In addition to the well-known states of 12C, (1975AS06) report the population of states with Ex = 18.3 ± 0.3, 20.6 ± 0.3 and 21.9 ± 0.3 MeV [broad], of a broad maximum at ≈ 27 MeV, and possibly also of states at Ex = 10.8 ± 0.2 and 11.8 ± 0.2 MeV. (1977CH1L) report two structures at Ex = 26 ± 1 and 29 ± 1 MeV, with Γ = 2 ± 1 and 4 ± 1 MeV, and determine L = 3 in the excitation of 12C*(18.4).
Reaction (b) has been studied in a kinematically complete experiment at Ed = 5.00 to 5.50, 9.20 and 9.85 MeV by (1973SA03) and also at Ed = 5.1 to 6.5 MeV [see the discussion in (1975AJ02)]. See also 13C and 13N in (1976AJ04). For pion production see (1977BR33, 1978PE12). See also 14N in (1976AJ04, (1981AJ01). See also (1975KI1G, 1979AZ1B), (1974AD1B, 1975SC1V) and (1974CH58, 1975GU10, 1975MA23, 1976CH03, 1977DM1A, 1977KU07, 1977VA03, 1978GH03, 1978HA1Q, 1978MA34, 1978NI1A, 1978ZE03, 1979CH06, 1979LA02; theor.). For reaction (c) see (1979HE06).
Angular distributions of elastically scattered tritons have been determined at Et = 1.0 to 20.04 MeV: see (1975AJ02).
Angular distributions of 3He ions have been measured in the range E(3He) = 2 to 217 MeV: see (1968AJ02), Table 12.22 (in PDF or PS) in (1975AJ02) and Table 12.17 (in PDF or PS) here. Parameters of observed 3He groups are displayed in Table 12.19 (in PDF or PS).
Angular distributions of the 3He groups to 12C*(15.11, 16.11, 16.58, 19.56) have been compared with those for the tritons to 12N*(0, 0.96, 1.19, 4.25) in the analog (3He, t) reaction: the correspondence is excellent and suggests strongly that these are T = 1 isobaric analog states (1969BA06: E(3He) = 49.8 MeV). See also Tables 12.12 (in PDF or PS) and 12.19 (in PDF or PS). The states reported by (1977BU03) at E(3He) = 130 MeV [see Table 12.19 (in PDF or PS)]: 12C*(4.4, 15.2, 18.4, 18.9, 21.3, 23.5, 25.9, 28.8) are all stated to correspond to E2 transitions: their strengths add up to 46% of the EWSR (energy-weighted sum rule). The quadrupole deformation parameter β2 = 0.30 can account for both the elastic and inelastic data providing that the ratio of the s.o. and central deformation βs.o./βcent is energy dependent (E(3He) = 20.5 - 33 MeV) (1977KA25). See also (1975AJ02). For pion production see (1976WA10).
See also 15O in (1976AJ04, 1981AJ01), (1975AU01), (1976RO1L, 1978BE1H) and (1974CH58, 1974KU15, 1975MA23, 1977DM1A, 1977GE1E, 1977KU07, 1978ZE03; theor.).
Angular distributions have been measured at many energies up to 1.37 GeV: see Tables 12.24 (in PDF or PS) in (1968AJ02), 12.22 (in PDF or PS) in (1975AJ02) and 12.17 (in PDF or PS) here. Parameters of observed states of 12C are displayed in Table 12.19 (in PDF or PS). Jπ assignments have also been suggested for 12C states with 9.6 ≤ Ex ≤ 39.3 MeV on the basis of their decay into 3α-particles: see (1973JA02; Eα = 90 MeV). The quadrupole deformation, β2, is -0.29 ± 0.02 (1971SP08), -0.30 ± 0.02 (1976PA05), 0.4 (1977BU19), 0.46 (1973SM03); β3 = 0.24 (1973SM03), 0.23 (1977BU19).
Angular correlation measurements (α1γ4.4) have been carried out for Eα = 10.2 to 104 MeV: see (1975AJ02, 1978AL20, 1978RI03). See also (1976AL23, 1976GU1B). The relative population of magnetic substates has been studied by (1970HA15, 1972BU09). Alpha-alpha correlations from 12C*(14.1) to 8Beg.s. lead to an assignment of Jπ = 4+ for that state (1977MC07). See also (1978RI03).
At Eα = 104 MeV, the sum of the E2 strength in the dominant decay channels [α0 + α1 + p0] for 20 < Ex < 30 MeV exhausts less than 15% of the EWSR (energy-weighted sum rule) (1978RI03). At Eα = 150 MeV, the observed isoscalar E2 strength is (6 ± 2)% of EWSR (1976KN05). See also (1976KIZN). The yields of the 12.71 and 15.11 γ-rays have been measured for Eα = 22 to 27 MeV: strong structures are observed [see 16O]. The yield of γ15.1 is 1 to 20% of that for γ12.7 (1975SP04). Measurements of the radiative widths for 12C*(7.7, 9.6) are reported in Table 12.8 (in PDF or PS) (1974CH32, 1976MA46).
Reaction (b) has been studied for Eα up to 700 MeV: see (1975AJ02). See also (1977YA1A, 1979DO04). For pion production see (1976WA10, 1977BR33, 1978PE12). For reaction (c) see (1976WO11).
See also (1974YOZO, 1976YU01, 1978FR1L, 1978SH1H, 1979AR05), (1975GR41, 1975SC1V, 1976OG1A, 1976SI1E, 1977HA1P, 1977MA2E, 1977ST1G, 1978BE1H, 1978MO29) and (1974CH58, 1974KU15, 1975CO1H, 1975GO02, 1975MA23, 1975RU10, 1975ST10, 1976AV05, 1976BA1N, 1976CU07, 1976HU07, 1976ME20, 1976PA25, 1976SAZC, 1977AL01, 1977BA12, 1977CL1D, 1977DM1A, 1977GE1E, 1977HO1H, 1977SA1P, 1977SA19, 1977TU1E, 1977VI06, 1977VI1C, 1977ZE01, 1977ZE1C, 1977ZE1D, 1978AH03, 1978FR1F, 1978FR1H, 1978SU01, 1978SU1G, 1978YO1F, 1978ZE03, 1979CH06, 1979DY1F, 1979LA02, 1979MO07; theor.).
The elastic scattering in reaction (a) has been studied at E(6Li) = 4.5 to 40 MeV [see (1975AJ02)], at 4.5 to 13 MeV (1976PO02), 50.6 MeV (1976CH27) and 59.8 MeV (1975BI06; also to 12C*(4.4, 7.7)), and at E(pol. 6Li) = 20 and 22.8 MeV (1976WE10). See also (1977SC1B: E(6Li) = 100 MeV) and (1976WE10, 1978DR07, 1978MA13) in 18F (1978AJ03, 1983AJ01). (1974BI04: E(6Li) = 36.4 and 40 MeV) have measured the inelastic angular distributions to 12C*(4.4, 7.7, 9.6, 10.8, 11.8, 12.7, 13.4, 14.1) and have calculated deformation parameters under various assumptions. For the α-decay of 16O states see (1977CU1B).
The elastic scattering in reaction (b) has been studied at E(7Li) = 4.5 to 36 MeV [see (1975AJ02)], at 4.5 to 13 MeV (1976PO02), 36 MeV (1976CO23) and at 89 MeV (1979BR04; also to 12C*(4.4); β22 = 0.51 ± 0.02). See also (1978DR07) in 19F (1983AJ01). See also (1971SC21, 1975GR41, 1976OG1A, 1978FI1E) and (1975TH1C, 1976AM01, 1976ST22, 1977KU07, 1978MA1B, 1978ME14, 1978NO08, 1978PE1C, 1979BE59; theor.).
Elastic scattering angular distributions have been obtained at E(9Be) = 14, 20 and 26 MeV (1979JA04, 1979UN01), 39.7 and 43.8 MeV (1979MA21; also to 12C*(4.4)) and at E(12C) = 12, 15, 18 and 21 MeV (1970BA49). For excitation function measurements see (1978MA44); for fusion cross sections see (1978CH02). See also (1976ECZZ, 1977IG1D, 1977PE1B), (1976OG1A, 1978TA1B) and (1978PA1B; theor.).
Elastic angular distributions for reaction (a) have been measured at E(10B) = 18 MeV (1968VO1A, 1969VO10) and 100 MeV (1975NA15, 1977TO02; also to 12C*(4.4, 9.6)). Elastic angular distributions in reaction (b) have been studied at E(12C) = 15, 17, 20 and 24 MeV (1974BO15), 16, 18, 22 and 24 MeV (1975DU11) and 87 MeV (1971LI11) and at E(11B) = 28 MeV (1968VO1A, 1969VO07, 1969VO10; also to 12C*(4.4) as well as to several 11B states). See (1978FR20) for differential cross section measurements in the range E(11B) = 18.8 to 34.1 MeV and (1976ST12, 1977HI02) for fusion cross section measurements. See also (1973BR1C, 1975AJ02), (1976AR1H, 1978RO1D; astrophys.) and (1975RE04, 1978AV1A, 1978VA1A; theor.).
Angular distributions have been measured at E(12C) = 10 to 20 MeV (1977HI1D, 1977KO1Q, 1977KO1W, 1978ER1D: g.s.), 10 to 37.6 MeV (1973EM03, 1975EM01: g.s. + g.s., g.s. + 4.4, 4.4 + 4.4), 17.6 to 27.5 MeV (1977CI01: g.s.), 40 to 60 MeV (1973WI09: g.s. + g.s., g.s. + 4.4), 30 to 50 MeV (1978CO20: g.s.), 70 MeV (1971KO11, 1975KO1E: g.s., 4.4, 4.4 + 4.4, 9.6), 70.7 to 126.7 MeV (1976WI14, 1977ST1Q, 1979ST10: g.s., 4.4, ((4.4 + 4.4) + 9.6)), 87 MeV (1971LI11: g.s.), 98.2 MeV (1977ST1Q: 7.65, 9.64, 14.07), and 114 and 174 MeV (1973AN22: g.s., 4.4, 7.7, 9.6, 14.1, 19.6).
The relative population of elastic and inelastic channels is very energy dependent: see, e.g., (1975AJ02) and (1975EM02, 1977BR18, 1977CI01, 1977CO05, 1977CO1P, 1977KO1Q, 1977KO1V, 1977KO1X, 1978CA1K, 1978CO20, 1978ER1D, 1978JA1D, 1979CL06). Total cross sections at 1.55 and 2.89 GeV/c/A are reported by (1978JA16). See also (1976SP07, 1978CO1L, 1978KO1L, 1978SA05, 1979COZS, 1979HA1P, 1979HEZX, 1979NA02) and (1974FO1F, 1978RO1D, 1978RO1L; astrophys.) and (1974VE05, 1975FR13, 1976AR14, 1976CU03, 1976CU07, 1976MA45, 1976ZI01, 1977AB1B, 1977BA3E, 1977CH11, 1977CI1C, 1977CL1D, 1977FI1C, 1977FR1H, 1977FR12, 1977FR1L, 1977KI1L, 1977LO1H, 1977PA28, 1977PA1H, 1977RO1K, 1977SA09, 1977SA10, 1977WA1Q, 1978AB1C, 1978AR1H, 1978AV1A, 1978BE1R, 1978BI1G, 1978CH10, 1978DA1G, 1978FI1G, 1978FR1F, 1978FR1H, 1978FR1N, 1978KO14, 1978SC1G, 1978SC1E, 1978TA13, 1978TA1P, 1978TA1B, 1978TA19, 1978TA1T, 1978TO12, 1978VA1G, 1978VA1A, 1978WI05, 1979AB02, 1979CH06, 1979CO06, 1979GO1P, 1979HA07, 1979HE1H, 1979KO11, 1979LAZY, 1979MO1J, 1979NA03, 1979PH01, 1979PI03, 1979TA02, 1979TA1K; theor.).
Angular distributions for reaction (a) have been studied at E(12C) = 15, 19, 20 → 36 and 87 MeV [see (1975AJ02)] and at E(12C) = 20.0 to 35.5 MeV (1978CH29: g.s. and 4.4 - the latter from 30 MeV) and E(13C) = 12 MeV (1976WE28, 1977GU07: g.s.) and 36 MeV (1976WE21: g.s.). Elastic angular distributions in reaction (b) are reported at E(12C) = 12 to 20 MeV (1972BO68). For yield measurements see (1975AJ02) and (1976ST12, 1976WE28, 1977GE1G, 1978CH29, 1978LE1N). See also (1974GO1L, 1975VO1B, 1977WI1C), (1978RO1D; astrophys.) and (1975DE09, 1977IM1A, 1977TR1A, 1978AV1A, 1978CH30, 1978IM1A, 1978PA1B, 1978TA1B; theor.).
Angular distributions have been measured at E(14N) = 21 to 88 MeV [see (1975AJ02)], 37 to 58.3 MeV (1978CO20: g.s.) and at 53 MeV (1976ZE04: g.s.), 65, 84 and 88 MeV (1971KO11, 1975KO1E: g.s., 4.4, 9.6) and 155 MeV (1975NA11, 1975NA15, 1977TO02: g.s., 4.4, 9.6). See also (1977MO1A) and 14N in (1976AJ04). For fusion cross sections see (1976ST12, 1977KO1V, 1977SW02, 1978CO20, 1979GO09, 1979GO11). Reaction (b) has been studied for E(15N) = 31.5 to 47 MeV (1978CO20). See also (1977PH1C). See also (1978DA1E), (1975VO1B, 1976LE1F, 1978TS04), (1978RO1D; astrophys.) and (1975DE09, 1975MO23, 1975RA33, 1976AM01, 1977BA3E, 1977MA11, 1978AV1A, 1978CU1C, 1978CU1E, 1978CU06, 1978FR1N, 1978HO13, 1978KA14, 1978VA1A, 1979NA03; theor.).
Angular distributions have been measured at E(16O) = 20 to 168 MeV [see (1971AJ02, 1975AJ02, 1977AJ02)] and at E(16O) = 17.29 to 23.14 MeV (1976CH13), 30.8 to 33.9 MeV (1978SC06), 31.7 to 52.7 MeV (1978JA1H; also 12C*(4.4) from 46 MeV), 46 MeV (1976SP01; also involves various states in 16O), 52.0 MeV (1977SH16; also excited 16O states), 55.3, 56.7, 65.8 MeV (1978KA13; also excited 16O states), 59.6 to 61.2 MeV (1978SH01; not g.s.: 12C*(4.4)), 65 and 80 MeV (1973GU12; also 12C*(4.4) and excited 16O states), 84 MeV (1978BO11; only 12C*(4.4)), 80 to 122 MeV (1977CO20), and at 315 MeV (1979DO01; not g.s.: 12C*(4.4, 14.1, 25.3 - 26.7)), and at E(12C) = 65 MeV (1978BO11; also 12C*(4.4)) and 76.8 MeV (1977MO1A, 1977MO1H). See also (1978MA1R) and 16O in (1977AJ02, 1982AJ01).
(1979DO01) present evidence for the excitation of giant resonances in a number of nuclei including 12C: 12C*(25.3 - 26.7) (Γ ≈ 4 MeV) contain 25+15-10% of the E2 strength. (1978BO11) have measured the m-state populations in the transition to 12C*(4.4) at E(12C) = 65 MeV and E(16O) = 84 MeV. See also (1977DE1P). For reaction (b) see (1974WI05, 1979FU02, 1979SC10). See also (1975AJ02).
For fusion cross section measurements see (1976CU04, 1976EY01, 1976FR20, 1976SP03, 1977BR38, 1977KO1V, 1977NA23, 1978CH15, 1978FE04, 1978TA11, 1979KO03). For other yield measurements see (1975SH24, 1976CH13, 1976SP01, 1977CO20, 1977TA03, 1978JA04, 1978KA13, 1978MA22, 1978MA32, 1978SC06, 1978SH01, 1979FRZX, 1979FU02, 1979JAZY, 1979TA05). See also (1978MA1R). A number of resonances are observed. See also 28Si in (1978EN06).
See also (1977QU1A, 1978CI06, 1978CL1E, 1978KA1L, 1978LAZZ, 1979GAZV), (1976CU04, 1978RO1D; astrophys.), (1973BR1C, 1975GR41, 1975VO1B, 1978KO1L, 1978LE1T, 1978TS04, 1979CH07) and (1974SA1M, 1974VE05, 1975CH08, 1975VE12, 1976BA52, 1976CH1M, 1976YO01, 1977BA28, 1977BA3E, 1977CH11, 1977CL1D, 1977FR12, 1977JA1E, 1977MA1V, 1977MA1X, 1977MO1J, 1977PA1G, 1977RO1N, 1978AB1C, 1978AV1A, 1978BA53, 1978BI1G, 1978FR1N, 1978GO07, 1978MA28, 1978MA22, 1978MA50, 1978TA16, 1978TA1B, 1978VA1A, 1979KR07, 1979NA03, 1979STZU, 1979TA07, 1979TA1K, 1979TA12; theor.)
The elastic scattering angular distributions have been measured at E(17O) = 30.5 and 33.8 MeV (1978CH03) and 35 MeV (1967GO1A) and at E(18O) = 32.3 and 35 MeV (1978CH03), 35 MeV (1967GO1A) and 47.5, 55 and 57.5 MeV (1976WE05). Fusion cross sections have been measured for E(17O) = 16.9 to 33.8 MeV (1976EY01) and 34 to 80 MeV (1978HE18) and for E(18O) = 17.5 to 35.0 MeV (1976EY01), 50 MeV (1978HE18) and 100 MeV (1978CO07). See also (1976SP07, 1978CH03, 1978FR05, 1979CH07, 1979GAZV: yieldmeasurements), (1974GO1L, 1978LE1T, 1978TS04) and (1977BA3E, 1978BI1G, 1978PA1B, 1978VA1A, 1979KR07, 1979NA03, 1979PAZY; theor.).
Elastic scattering angular distributions have been measured at E(19F) = 40, 60 and 68.8 MeV (1968VO1A, 1969VO10, 1972SC03). See also (1976SP07, 1977KO38: fusion cross section at E(19F) = 92 MeV), (1973BR1C, 1975GR41, 1975VO1B) and (1977BA3E, 1978BI1G, 1978HO13, 1978VA1A, 1979NA03; theor.).
Elastic angular distributions for reaction (a) have been measured at E(12C) = 37 MeV (1974VA18) and E(20Ne) = 65.7 MeV (1975DO06, 1978DO01). For yield measurements see (1977CO1Q, 1977PR1F, 1978DO01, 1979FOZY). See also (1977SC1G), (1978RO1L; astrophys.) and (1976VA12, 1977OS02, 1978VO06; theor.).
See (1978CL1E, 1979DAZT). See also (1978TA1B, 1979TA1K; theor.).
The angular distribution of the transition to 12C*(4.4) has been measured at E(12C) = 82 MeV (1977BE42). See also (1977SC1G) and (1978VA1A; theor.).
Elastic angular distributions have been studied at E(12C) = 19 to 36 MeV (1977CH25), 24, 27 and 30 MeV (1977EC04), 40.2 MeV (1975RA33), 49.3, 70 and 83.5 MeV (1971KO11) and 186.4 MeV (1977DE23) and at E(28Si) = 58.3 to 116.7 MeV (1978CL02, 1979OS01). For yield measurements see (1978BA02, 1978CL02, 1979KUZX). See also (1978TA1B) and (1977ZI1C, 1979TA1K; theor.).
Elastic angular distributions are reported at E(12C) = 35.8 MeV (1978GE14) and E(32S) = 73.3 to 128.3 MeV (1979OS01: back angles).
The elastic scattering in reactions (a), (c) and (d) has been studied at E(12C) = 51.0, 49.9 and 49.9 MeV, respectively (1979RE03). See also (1979OS01). For reaction (b) see (1978BA26; theor.). For yield measurements see (1978RE06, 1979KU02, 1979RE03).
The decay is mainly to the ground state via an allowed transition. Branching ratios to other states of 12C are displayed in Table 12.20 (in PDF or PS). The half-life of 12N is 11.000 ± 0.016 msec (1978AL01). See also the earlier values in Table 12.28 (in PDF or PS) of (1968AJ02). Since transitions to 12C*(0, 4.4) are allowed Jπ(12N) = 1+.
A recent measurement of the ratio of the branching ratios 12N/12B for the decays to 12C*(4.4) is R = 1.56 ± 0.05 (1978AL01). This leads to the following values for the mirror asymmetries of 12B and 12N for decay to 12C*(0, 4.4): δ4.4 = +0.044 ± 0.034, δg.s. = +0.129 ± 0.008 (1978AL01). See also (1975AJ02) for earlier measurements. These values in turn lead to second class current (SCC) contributions δ0SCC = -0.006 ± 0.038 and δ1SCC = -0.047 ± 0.037, which are consistent with zero (1978AL01).
The shapes of the β-spectra of 12B and 12N have been analyzed to give the following values for α- - α+: (+0.98 ± 0.09)%/MeV (1977KA24), (+0.86 ± 0.24)%/MeV (1977WU01) and (+0.302 ± 0.062)%/MeV (1977SU1F). (1978BR18) find α+ = -0.273 ± 0.039%/MeV in agreement with the results of (1977SU1F: -0.277 ± 0.052%/MeV), These measurements are in agreement with CVC and with the absence of second class induced tensor currents. See also (1976CA29, 1978MO02, 1979KO12; theor.). See also (1975SU01, 1976SU1C, 1977DE11), (1973MIYZ, 1974AD1B, 1976BE1E, 1977GA1E, 1977RI08, 1977TE1B, 1978CA1H, 1978LE02, 1978RA2A, 1978WE1J, 1979DO1A) and (1975BE24, 1975DO10, 1975DO1D, 1975KU20, 1975MO1F, 1975RH1A, 1975WI1E, 1976KH05, 1976MO1G, 1976SU09, 1976YO1D, 1977BE2A, 1977HW01, 1977KU1E, 1977OK1A, 1977WA1F, 1977YA1D, 1978BE1V, 1978BE58, 1978KU1A, 1978MO02, 1978SE1B, 1978SZ07, 1979DE15, 1979SZ02; theor.).
The decay of the giant resonance in 13C takes place predominantly to 12C*(15.1, 16.1) [and their analogues in 12B]. Below Eγ = 21 MeV transitions to 12C*(0, 4.4) are dominant (1975PA09). See also (1976CR1C, 1977WO04), (1977MA06; theor.), (1975AJ02) and 13C in (1981AJ01).
At Eπ+ = 34 MeV the population of 12C*(4.4) is more than 10 times that of 12Cg.s. (1978DO1F). See also (1975HU1D; theor.).
Angular distributions of the d0 and d1 groups to 12C*(0, 4.4) have been measured at Ep = 8, 12, 17, 50 and 54.9 MeV [see (1975AJ02)], 16.7 and 17.7 MeV (1977GU14) and 200 to 500 MeV (1979KA1R). See also (1978BA1R, 1978IG1A; prelim.: 650 and 800 MeV) and (1979CA1A). Angular distributions have also been measured for the groups to 12C*(12.7, 15.1, 16.1) at Ep = 50 MeV (1970SC02) and 54.9 MeV (1968TA08). 12C*(14.1) is not excited, consistent with Jπ = 4+ (1970SC02, 1974PA01). At Ep = 62 MeV, (1974PA01) report the excitation of states with Ex = 15112 ± 5, 16110 ± 5 [< 20], 17760 ± 20 [80 ± 20], 18800 ± 40 [80 ± 30], 21500 ± 100 [< 200] and 22550 ± 50 [< 200] keV [the numbers shown in brackets are Γc.m., in keV]: ln = 1 for all states except 12C*(21.5) and (22.55) for which lp = (1) and ≠ 1, respectively. Spectroscopic factors are derived by (1968TA08, 1970SC02, 1974PA01): see (1977AD02).
In a kinematically complete experiment at Ep = 7.9 to 12.5 MeV, it is found that sequential decay via states in 13C and 13N is strongly involved in reaction (b). Near Ep = 12.5 MeV there is some indication of sequential decay via singlet deuteron formation (1971OT02). See also (1975AJ02), 13C, 13N, 14N in (1981AJ01) and (1978MA34; theor.).
Angular distributions have been studied at Ed = 0.41 to 28 MeV [see (1975AJ02)] and at Ed-bar = 13 MeV (1978DA17: t0, t1, t2), Ed = 24.1, 26.2 and 27.5 MeV (1977LI02: t to 12C*(12.71, 15.11, 16.11) and Ed-bar = 29 MeV (1979CO08: t to 12C*(0, 4.4, 12.71, 15.11, 16.11); see also 13C(d, 3He) in 12B). (1977LI02) find an isospin mixing parameter, β, of 0.07 ± 0.03 for the two 1+ states 12C*(12.71, 15.11) and a charge-dependent matrix element of 180 ± 80 keV (1977LI02), 120 ± 30 keV (1979CO08); both are lower than the value previously obtained in this reaction, 250 ± 50 keV (1972BR27). If the j = 1/2 component is excluded, which appears to be unwarranted, the charge dependent matrix element is 140 ± 40 keV (1979CO08). See also reactions 21, 22, 44, 50, 74 and 86. See also 15N in (1981AJ01) and (1975ZA06, 1977AD02).
Angular distributions have been measured at many energies up to E(3He) = 45 MeV [see (1968AJ02, 1975AJ02)] and at 18 and 20 MeV (1977AD07; α0, α1) and 29.2 MeV (1976FU1F; α1). Angular correlations of α-particles and 4.4 MeV γ-rays have been studied at E(3He) = 4.5 MeV (1962HO13) and 29.2 MeV (1976FU1F) and for αγ15.1 at 9.4 and 11.2 MeV (1969TA09).
A study of reaction (b) leads to Γα/Γ for 12C*(15.11) = 4.1 ± 0.9%; together with the other parameters for the decay of the state (see Table 12.8 (in PDF or PS)) this leads to Γα = 1.8 ± 0.3 eV. If this isospin forbidden α-width is the result of the mixing between the 1+ states 12C*(12.71, 15.11) [T = 0 and 1, respectively] via a charge dependent interaction, the matrix element is 340 ± 60 keV (1974BA42). See also reactions 21, 22, 44, 50, 73 and 86. For the decay of 12C*(12.7, 15.1) see Table 12.8 (in PDF or PS) (1970RE09). See also (1976STYX, 1978SM1B) and (1977TA06; theor.).
At E(7Li) = 34 MeV angular distributions have been observed for the reactions to 12C*(0, 4.4) + 7Li*(g.s., 0.48) and 8Li*(0, 0.95) in all combinations. While 12C*(0, 4.4) are dominant in the two spectra, 12C*(7.7, 9.6) and, in reaction (a) at E(6Li) = 36 MeV, 12C*(12.7) are also populated (1973SC26).
Angular distributions for reaction (a) have been measured at E(16O) = 13 and 14 MeV (1976DU04), 14, 17 and 20 MeV (1968KN1A, 1971BA68) and 41.7 and 46.0 MeV (1973DE21). See also (1975SE03). Angular distributions for reaction (b) are reported at E(17O) = 29.8 and 32.3 MeV (1977CH22, 1978CH16) while reaction (c) has been studied at E(18O) = 15, 20 and 24 MeV (1971BA68, 1971KN05) and 31.0 MeV (1978CH16). In all cases the 12Cg.s. is involved as well as various states in the residual nucleus: see 13C in (1981AJ01), 17O in (1982AJ01) and 18O in (1978AJ03, 1983AJ01) and 19O in (1978AJ03, 1983AJ01). See also (1978PA1D, 1978SC1E; theor.).
Angular distributions have been measured at Ep = 14.5, 18.5 and 39.8 MeV: see (1975AJ02). At Ep = 54 MeV angular distributions are reported to two states at Ex = 27.57 ± 0.03 and 29.63 ± 0.05 MeV [Γc.m. ≲ 200 keV]: their identification as the first T = 2 states is supported by the similar angular distributions to the first two T = 2 states in 12B, reached in the (p, 3He) reaction [see reaction 20 in 12B]. The lower T = 2 state is well fitted by L = 0; the angular distribution to 12C*(29.63) is rather featureless. It is suggested that its shape is somewhat more consistent with L = 0 than with L = 2 (1976AS01). [(1976BA24) has suggested that the second T = 2 state in A = 12 may have Jπ = 0+.] It is not excluded that the group to 12C*(29.63) may be due to unresolved states (1976AS01). (1976AS01) report Γp/Γ ≈ 0.3 ± 0.1 and Γα1/Γ < 0.1 for the first T = 2 state and Γp/Γ = 0.8 ± 0.2, Γp0/Γ ≈ 0.4 and Γα/Γ ≈ 0.2 for 12C*(29.63). (1978RO08) report Ex = 27595.0 ± 2.4 keV, Γ ≤ 30 keV for the first T = 2 state and calculate the decay properties for two values of total width, 0 and 30 keV. Branching ratios for the decays to 8Be(0) + α; 11B*(0, 2.12, 4.45, 5.02, 6.74 + 6.79) + p; and 10B(0) + d are, respectively, 10.5 ± 3.0, 3.0 ± 2.2, 8.0 ± 2.3, 0 ± 3.3, 8.4 ± 3.2, 8 ± 5, and 2.8 ± 2.0% (1979FR04).
Angular distributions leading to the ground states in reaction (a) have been measured at E(16O) = 20, 25 and 30 MeV (1973SC24, 1975SC35) and 32 MeV (1968GO01: see (1975SC35)). For reaction (b) see (1972EY01). See also (1978KA23; theor.).
See 13C, 14N in (1976AJ04) and (1979ME1E; theor.).
Angular distributions of the t0 group have been measured at En = 14 - 15 MeV: see (1968AJ02). At En = 18.2 MeV reaction (b) takes place predominantly via sequential decay processes involving 12C*(9.6, 10.8, 11.8) (1976TU04). See also 15N in (1981AJ01).
See (1971WE05). See also (1976DO12; theor.).
Angular distributions have been studied at Ep = 7.53 to 44.6 MeV [see (1975AJ02)], at 50 MeV (1970SC02: to g.s., 4.4, 12.7, 14.1, 15.1, 16.1) and at 51.9 MeV (1976YO03: to 15.1, 16.1). The results of (1970SC02) strongly indicate Jπ = 4+ for 12C*(14.1). At the highest energy (1976YO03) have measured the angular distributions to the first two T = 1 states in 12C and to the analog states in 12N, in the (p, t) reaction. See also 15O in (1981AJ01).
Observed α-particle groups are shown in Table 12.19 (in PDF or PS). Angular distributions have been measured at energies up to 28.5 MeV [see (1968AJ02, 1975AJ02)] and at Ed = 2.70 to 2.76 MeV (1977KO33: α0, α1, α2), 15 MeV (1976LU1A: α0, α1, α2) and 40 MeV (1976VA07: α0, α1 and α to 12C*(12.71, 14.08, 19.5, 20.6, 22.5)). Analysis of the angular distributions with a one-step, ZRDWBA, leads to Jπ = (1, 2, 3)+, (2, 3)+ and (2, 3)+, respectively for 12C*(19.5, 20.6, 22.5) (1976VA07: spectroscopic factors calculated for all observed transitions). For a comparison of the relative strengths of 12C*(12.7, 15.1) at Ed = 40 MeV see (1974VA15). See also reactions 21, 22, 44, 50, 73 and 74. For reaction (b) see (1972FA07). See also 16O in (1977AJ02), (1975OL1A; applications) and (1978BE1H).
See 16O in (1977AJ02).
At Eα = 42 MeV angular distributions of 6Li ions corresponding to transitions to 12C*(0, 4.4) have been measured by (1964ZA1A). For reaction (b) see 16O in (1977AJ02).
See (1976PA22). See also (1977SP06) and 15N in (1981AJ01).
Angular distributions of α0 and α1 have been measured for Ep up to 18 MeV [see (1968AJ02)], at Ep = 2.99 to 5.14 MeV (1977JA11) and at six energies in the range Ep = 19.85 to 43.35 MeV (1971GU23). At Ep = 43.7 MeV the angular distributions to the 0+ states 12C*(0, 7.65, 17.76) are fitted by L = 1, and L = 3 is consistent with the distributions to 12C*(14.1, 16.1) [Jπ = 4+ and 2+, respectively] (1972MA21). The lifetime of 12C*(4.4) τm = 65 ± 9 fsec (1970CO09). The energy of the second excited state of 12C is 7654.2 ± 1.6 keV. The weighted average of this and previous values leads to Ex = 7654.6 ± 1.1 keV, a value which leads to a sharply reduced rate for the (ααα) process (1973MC01). See also (1966YO1A), (1977RO1H; astrophys.), (1975KU1L; theor.) and (1979ZY02) in 16O in (1982AJ01).
At Eα = 42 MeV angular distributions have been obtained for all four of the transitions: 12Cg.s. + 7Li*(g.s., 0.48) and 12C*4.4 + 7Li*(g.s., 0.48) (1968MI05).
See (1975AJ02) and (1975SK06) in 16O (1977AJ02).
For reaction (a) see (1968AJ02). Reaction (b) appears to proceed primarily via excited states of 13N and 16O to 12C*(4.4): see (1971EP03: Ep = 46.8 MeV) and (1972BO71: Ep = 50 MeV). See also (1975AJ02) for unpublished measurements and (1976GO1E; theor.).
Angular distributions have been measured at Ed = 12.7, 13.6 and 14.6 MeV (1974GA30, 1975GO09; g.s.), Ed-bar = 16 MeV (1976JA1G; g.s.), Ed = 35 MeV (1975BE01, 1976NA19; g.s., 4.4), 50, 65 and 80 MeV (1978BE1T: g.s., 4.4, 14.1: ZRDWBA) and 80 MeV (1978OE02; to g.s., 4.4, 7.7, 9.6, 14.1, and broad (or unresolved) structures at 14.1 ± 2.6, 19.5 ± 1.5 MeV: ZRDWBA and FRDWBA). (1978BE1T, 1978OE02) report relative Sα. The relative Sα are strongly influenced by the choice of bound state parameters: see (1978BE1T), and compare with (1978OE02). Earlier studies at Ed = 14.6, 19.5, 28 and 55 MeV are listed in (1975AJ02). See also (1973FO1A, 1978BE1H), (1977KU1H, 1978TA1F; theor.) and 18F in (1978AJ03).
Angular distributions have been studied at E(3He) = 25.5 MeV (D. Pisano, Yale Ph.D. thesis [P.D. Parker, private communication]: 12C*(0, 4.4) + 7Be*(0, 0.4)), 30 MeV (1970DE12: (12C*(0, 4.4, 9.6) + 7Be*(0, 0.4), 12C*(7.7) + 7Beg.s.) and at 70 MeV (1976ST11: 12C*(0, 4.4) and 7Be*(0, 4.4); Sα are calculated). In the latter experiment 12C*(7.7, 9.6) are observed but they are weakly populated (1976ST11). (1975AU01) report the extraction of Sα, the α-particle pickup spectroscopic factor, using a FRDWBA analysis [E(3He) = 26 MeV]. See also (1975AJ02).
At Eα = 90 MeV angular distributions involving 12C*(0, 4.4) (reaction (a)) have been analyzed by PWIA and DWBA by (1976SH02): Sα = 2.9 ± 0.5 and 0.70 ± 0.23, respectively. At Eα = 65 MeV angular distributions involving 8Beg.s. (reaction (b)) and 12C*(0, 4.4, 7.7, 9.6, 14.1) have been measured by (1974WO1C, 1976WO11) [the ground state distributions have also been studied for Eα = 55 to 72.5 MeV]: Sα = 0.25, 1.07, 0.05, 1.40 for 12C*(0, 4.4, 7.7, 14.1). See also (1975AJ02) for earlier work, (1975HA1P, 1975IG1A, 1979BEZV) and (1977CH02; theor.).
See (1975SE03) and 17O in (1977AJ02). See also (1973BR1C).
Angular distributions have been measured at E(16O) = 23.9 MeV (1974SP06: g.s. + g.s.) and 51.5 MeV (1974RO04: 12C*(0, 4.4) and various 20Ne states). At Ec.m. = 17.5 MeV (reaction (a)) and 17 MeV (reactions (b) and (c)) angular distributions involving 12Cg.s. (reaction (a)), 12Cg.s. and 12C*(0, 4.4) (reactions (b) and (c)) as well as a number of states in 20Ne, 21Ne and 22Ne have been studied by (1977KA26). See reaction 25 in 20Ne (1978AJ03) for additional work. See also (1978BO1R; theor.).
The decay of the lowest T = 2 state of 16O to 12C*(0, 4.4) has been studied by (1973KO02). See also 16O in (1977AJ02).
See reaction 38 in 20Ne (1978AJ03).
Ground state angular distributions have been measured at Ed = 9 to 14.5 MeV (1964DA1B, 1967DE03, 1967DE14).
See 20F in (1978AJ03).
See (1975AJ02) and (1978DA1F).
Angular distributions have been reported at Eα = 22.8 to 25.4 MeV (1978SO10) and 90 MeV (1979BEZV, 1978BE1U, 1977BE2G). See also 16O in (1982AJ01).
See (1972MA36: E(16O) = 42 MeV). See also (1975AJ02).