(See Energy Level Diagrams for 12C)
Shell model: (1967SV1A, 1968BA1L, 1968DR1B, 1968FA1B, 1968FU1B, 1968GO01, 1968GU1C, 1968HA11, 1968RO1G, 1969GU1E, 1969GU03, 1969IK1A, 1969LA26, 1969MO1F, 1969SA1A, 1969SV1A, 1969WA06, 1969WO05, 1970AR21, 1970BE26, 1970BO33, 1970BO1J, 1970CO1H, 1970DE1F, 1970DO1A, 1970EI06, 1970GI11, 1970GU11, 1970KH01, 1970KO04, 1970KR1D, 1970LO1C, 1970RE1G, 1970RU1A, 1970RY1A, 1970SV1B, 1970WO12, 1971AR1R, 1971BO29, 1971GR16, 1971GU11, 1971NO02, 1971RO03, 1971ZO03, 1971ZO01, 1972AB12, 1972BE1X, 1972BO38, 1972BR1G, 1972FO1G, 1972JA18, 1972KR1D, 1972LE1L, 1972MS01, 1972RE03, 1972SA1B, 1972SU01, 1972VE01, 1973BO07, 1973EL04, 1973FR09, 1973HA05, 1973HA49, 1973KU03, 1973LO1C, 1973SA30, 1973YA1A, 1974HU1D, 1974KA11, 1974KU05).
Collective and deformed models: (1968HE1C, 1969AB05, 1969BA1R, 1969RU04, 1970DA13, 1970KH01, 1970SH1C, 1970SV1B, 1970TU01, 1970WE1B, 1971AR1R, 1971BO29, 1971CI03, 1971HO19, 1971SP11, 1971ZO03, 1971ZO01, 1972AB1C, 1972BE1X, 1972BO38, 1972FO1G, 1972HO56, 1972LE1L, 1973BO07, 1973CA16, 1973DO10, 1973FU1E, 1973KO1F, 1973LA35, 1973MS01, 1973YA1A, 1974AR04, 1974LE04, 1974TA19).
Cluster and alpha particle model: (1968FU1A, 1968HE1B, 1968PI1A, 1968TA1G, 1969AB1B, 1969BA1J, 1969BE1K, 1969BR1H, 1969HE1G, 1969HU1C, 1969IK1A, 1969KI02, 1969KO1K, 1969LE21, 1969NA1C, 1969SM1A, 1969TA1F, 1969TA1C, 1969WA06, 1969YA1A, 1970BA1Q, 1970BR35, 1970DE45, 1970EI05, 1970EI06, 1970EL01, 1970HU1F, 1970KO26, 1970LI24, 1970MC1D, 1970NE1F, 1970NO1A, 1970YU02, 1970ZI04, 1971AB07, 1971AB1B, 1971BA85, 1971BO20, 1971DA13, 1971DU06, 1971FR06, 1971FR15, 1971KH06, 1971KU1G, 1971NO03, 1971NO02, 1971OS04, 1971RA36, 1971RI1D, 1971SA1A, 1971TA13, 1971VI05, 1972AB1C, 1972AB11, 1972AB19, 1972AK10, 1972AN12, 1972AN15, 1972BA59, 1972DE03, 1972FR1B, 1972GR42, 1972HO56, 1972IK1A, 1972LE40, 1972RU13, 1972TU01, 1972VA40, 1972ZI03, 1972ZI05, 1973AB1G, 1973AB1A, 1973AN05, 1973BE1L, 1973CO13, 1973CO15, 1973FU1E, 1973HA57, 1973IK1A, 1973KH1A, 1973KU03, 1973LA35, 1973SA38, 1973YA1A, 1974AB05, 1974HO1Q, 1974JA24, 1974KA23, 1974KA11, 1974ME08, 1974SM1A, 1974SM04, 1974SU1B, 1974VA1N).
Special levels: (1966BR1D, 1967MA1B, 1968CE01, 1968LA1B, 1969GU03, 1969HA1G, 1969HA1F, 1969SO1E, 1969WO05, 1970AR21, 1970BO33, 1970BO1J, 1970DA13, 1970GO41, 1970GR27, 1970PE18, 1970RO20, 1970RU1A, 1971AR1R, 1971BE2B, 1971FA11, 1971FR15, 1971GR1V, 1971GR23, 1971GR38, 1971GR49, 1971MC15, 1971NO02, 1971RO03, 1971SE03, 1971VI05, 1971WA27, 1972AI01, 1972BE1X, 1972DE03, 1972EN05, 1972HA1R, 1972JA18, 1972SU01, 1972SU04, 1972VA40, 1973BO07, 1973CA1J, 1973IK1A, 1973KH1A, 1973KN1C, 1973MA1K, 1973MI1F, 1973SA30, 1973YA1A, 1974AR04, 1974HA1G, 1974IT1A, 1974KA11, 1975SH01).
Giant resonance: (1968BA1J, 1969DR05, 1969MA22, 1969RO26, 1969UB01, 1970FI1D, 1970FR1E, 1970GU12, 1971DU13, 1971GR23, 1971GU10, 1971SE03, 1971WA27, 1972KA33, 1972KE06, 1972MS01, 1972SU01, 1972NA05, 1973BA05, 1973DE53, 1973HA1Q, 1973MA1T, 1973MS01, 1973MS02, 1973PI06, 1973SU03, 1974CA1R, 1974FA1A, 1974MU13).
Electromagnetic transitions: (1968CA08, 1968LA1B, 1969AB05, 1969DR05, 1969HA1G, 1969HA1F, 1969LA26, 1970DO1A, 1970WE1B, 1971TA13, 1972AB12, 1972BE1X, 1972BE98, 1972BO38, 1972DE03, 1972NA05, 1973AL14, 1973BE1L, 1973BO07, 1973BO31, 1973CA16, 1973EL04, 1973HA49, 1973HA1Q, 1973KU1N, 1973LE1E, 1973SA30, 1974AB05, 1974FI03, 1974MU13).
Astrophysical questions: (1967SH1B, 1967WI1B, 1968DU1C, 1969TR1A, 1970OH1B, 1972CL1A, 1972KO1A, 1972UL1A, 1973AR1H, 1973AU1B, 1973AU1D, 1973AU1C, 1973BO1R, 1973CA1B, 1973CO1J, 1973CO1B, 1973DA1L, 1973GR1G, 1973IB1B, 1973RA1D, 1973SA1J, 1973SC1T, 1973SM1A, 1973TA1E, 1973TA1D, 1973TR1C, 1973TR1B, 1973UL1B, 1974AR1G, 1974BE1R, 1974BO2K, 1974DA1N, 1974LA1J, 1974LA1K, 1974PA1E, 1974SC1F, 1974SN1B, 1974TO1C, 1974WI1F, 1975FA1H, 1975TA1E).
Muon and neutrino capture and reactions: (1967EV1B, 1967HI1B, 1968FR1E, 1968FU1B, 1968HI1C, 1968KE1D, 1968RH1A, 1969DI1C, 1969OZ1A, 1969VA37, 1969WU1A, 1970BU1B, 1970CA1H, 1970CA1J, 1970FR1E, 1970HI09, 1970PR1H, 1971AG01, 1971BA96, 1971LA1J, 1971MO1Q, 1971MU20, 1971PI1D, 1971PL01, 1971PL1F, 1972CA08, 1972DE50, 1972KE06, 1972LO1J, 1972MI15, 1972OC01, 1972UB01, 1973BA68, 1973BE51, 1973BE38, 1973CH16, 1973DO04, 1973KI12, 1973KU1N, 1973MU04, 1973MU11, 1973SA1U, 1974DE1V, 1974DO1C, 1974DU02, 1974IM1C, 1974KA1Q, 1974KO1M, 1974PO05, 1974VO12, 1975SU1G).
Pion capture and pion reactions: (1965CH12, 1965GI10, 1967FO1A, 1967KO1B, 1967LE1D, 1967MI1B, 1968AG1A, 1968AG1C, 1968BA1M, 1968BA48, 1968BA61, 1968BE1F, 1968BI1B, 1968CH1D, 1968DA1G, 1968ER1A, 1968GO1L, 1968KE1D, 1968KO1B, 1968KO1C, 1968NO1A, 1968RH1A, 1968ST1G, 1968TA1C, 1968UB1A, 1968VA1F, 1968WI1B, 1968WI1D, 1968ZE1A, 1968ZU1A, 1969AG1A, 1969BA1L, 1969CA1B, 1969CH1C, 1969CH19, 1969GO1C, 1969HE1E, 1969KO1F, 1969MA1C, 1969MO1E, 1969MO1G, 1969UB01, 1969WE05, 1970AB1A, 1970BA44, 1970BA1E, 1970BA1F, 1970BE1J, 1970BE1L, 1970BI1A, 1970BI10, 1970BJ1A, 1970CA1J, 1970CH1F, 1970CH1C, 1970EL1E, 1970ER1A, 1970GO28, 1970GO1F, 1970HI09, 1970HI10, 1970HI11, 1970JA23, 1970JO18, 1970KA1H, 1970KA1J, 1970KO23, 1970KO26, 1970KR1F, 1970MA18, 1970SC1P, 1970RA39, 1970ST21, 1970VA18, 1970WI21, 1971AM1A, 1971BI1K, 1971CA01, 1971CA1J, 1971DE31, 1971ED02, 1971FA09, 1971GO22, 1971GO29, 1971GR1X, 1971GR34, 1971GU11, 1971GU1H, 1971GU13, 1971IN1A, 1971KO30, 1971KO40, 1971LA1P, 1971LE14, 1971LE1Q, 1971LO1H, 1971MA1C, 1971MA29, 1971MA1P, 1971MA1T, 1971MA2A, 1971MO29, 1971PE1D, 1971RO14, 1971RO1L, 1971SE02, 1971SI36, 1971SK03, 1971SK02, 1971ST10, 1971TH05, 1972AB1H, 1972AL45, 1972BA13, 1972BE34, 1972BE36, 1972BI09, 1972BU1P, 1972DE07, 1972ER02, 1972ER1A, 1972FA03, 1972FA14, 1972FU1C, 1972FU22, 1972GI04, 1972HU1A, 1972HU1F, 1972JA1H, 1972KO31, 1972LA01, 1972LA10, 1972LA24, 1972LE03, 1972LE40, 1972MA1H, 1972MA32, 1972NI13, 1972SA10, 1972SC18, 1972SC40, 1972SE13, 1972SE1F, 1972SI24, 1972ST1H, 1972SW1A, 1972VA1K, 1972YO1C, 1973AL09, 1973AL1E, 1973AL14, 1973AL1A, 1973AN18, 1973AR1B, 1973AS1A, 1973BA2G, 1973BA1E, 1973BE2C, 1973BE2B, 1973BE2D, 1973BE47, 1973BR1J, 1973BU1B, 1973BU12, 1973CA1J, 1973CA17, 1973CA1L, 1973CL1J, 1973DA1G, 1973DE1Y, 1973DI08, 1973DO1F, 1973DU1C [η], 1973EI01, 1973FA1N, 1973GA20, 1973GE11, 1973GO18, 1973GO44, 1973GO41, 1973GR1J, 1973GR1F, 1973HA34, 1973HE30, 1973HO43, 1973HS1A, 1973HS1B, 1973HU1E, 1973JA1K, 1973KA1D, 1973KI03, 1973LA1N, 1973LA30, 1973LE1F, 1973LE22, 1973LI18, 1973LU1A, 1973MA10, 1973MA11, 1973MO1H, 1973MO20, 1973MO26, 1973NY04, 1973PE1E, 1973RO10, 1973RO1Q, 1973SE1E, 1973SH1E, 1973SI1N, 1973ST1K, 1973UB01, 1973WA1J, 1973WI1A, 1973YE02, 1973ZI1A, 1974AM01, 1974AZ02, 1974BA2E, 1974BO27, 1974BU1H, 1974CA21, 1974CA1P, 1974CA1G, 1974CA1Q, 1974CA25, 1974CL04, 1974CU1A, 1974DE1U, 1974EP02, 1974GA08, 1974GI08, 1974HA61, 1974HE1F, 1974HO29, 1974HU14, 1974KI01, 1974KO14, 1974KO07, 1974KU1K, 1974KU02, 1974LA12, 1974LA22, 1974LE1L, 1974LE1M, 1974LI1H, 1974LI08, 1974LI15, 1974MA37, 1974MI07, 1974MI06, 1974MI11, 1974MI12, 1974MU03, 1974NE18, 1974NI08, 1974OH01, 1974PI02, 1974ST1G, 1974TA18, 1974UL02, 1974VO12, 1974WI1P, 1975AR02, 1975GE02, 1975HE1M, 1975PI1E, 1975YA02).
Kaon capture and kaon reactions: (1968CH1F, 1969KU1B, 1971MA1T, 1972BA09, 1972BL10, 1972JU1A, 1972WA1F, 1973BA1Y, 1973BO1W, 1973BO1X, 1973BU1H, 1973CH1M, 1973FA1P, 1973GO41, 1974AL1J, 1974CA1H, 1974DE41, 1974HU1D, 1974HU1E, 1974MO1H, 1975KI1M).
Other topics: (1966BR1D, 1967KU1D, 1968BA1L, 1968BA1J, 1968BO1H, 1968FA1B, 1968GU1C, 1968IR1A, 1968LA1B, 1968LE1F, 1968NE1C, 1968RO1G, 1968TK1A, 1969AB05, 1969CH1A, 1969DR05, 1969GU03, 1969GR1A, 1969HO1M, 1969IR1A, 1969KE1B, 1969LA26, 1969LE21, 1969LO06, 1969MC1C, 1969NA1E, 1969RU04, 1969SH1A, 1969SO08, 1969SO1E, 1969VI1C, 1969VO1E, 1970BE26, 1970BO1M, 1970BO1J, 1970DR07, 1970EF01, 1970GR44, 1970HO1J, 1970JA02, 1970KA30, 1970KA1K, 1970PE18, 1970RE1G, 1970RU1A, 1970RY03, 1970SU1B, 1970VA07, 1971BA85, 1971BE2B, 1971BO1F, 1971FA11, 1971GR1V, 1971GR2C, 1971GR35, 1971GR49, 1971HO19, 1971KA14, 1971KU1G, 1971MC15, 1971NG01, 1971OS04, 1971SO11, 1971ST40, 1971TU04, 1971VO1E, 1971ZO03, 1972AB12, 1972AI01, 1972AN05, 1972AR13, 1972BR1G, 1972EL1E, 1972FO1G, 1972FR1B, 1972FR09, 1972HA57, 1972KO01, 1972KR11, 1972KR1D, 1972LE1L, 1972OC01, 1972PA32, 1972PN1A, 1972RE03, 1972SA1B, 1972ST02, 1972SU04, 1972TU01, 1972VE01, 1972ZI03, 1973AN05, 1973AV1C, 1973BA1Y, 1973BO31, 1973CL09, 1973DE07, 1973DZ1A, 1973ED1A, 1973EL04, 1973ER1C, 1973ER10, 1973FA1P, 1973FO1F, 1973FR09, 1973GR36, 1973HA05, 1973HA57, 1973KO26, 1973KU03, 1973KU1G, 1973LA35, 1973LO1C, 1973MA48, 1973MI1F, 1973PE05, 1973PO1D, 1973RA1E, 1973RO1R, 1973SA1T, 1973SI21, 1973UL01, 1973VA01, 1974AB05, 1974AR04, 1974AU1E, 1974CA1H, 1974DU11, 1974DZ03, 1974FA1A, 1974FI03, 1974HO1J, 1974HU1D, 1974HU1E, 1974IR04, 1974ME08, 1974MU13, 1974SI1F, 1974ZA01, 1975GR03, 1975KI1M, 1975KU01, 1975SH01, 1975ZI1D).
Ground state: (1968BA1L, 1968BO1H, 1968FA1B, 1969AB05, 1969AG03, 1969GU03, 1969KE1B, 1969LA26, 1969LE21, 1970EL01, 1970GR44, 1970ST19, 1971BO20, 1971BO29, 1971GR16, 1971GR2C, 1971RU14, 1971ZO03, 1972AB12, 1972AV1D, 1972BE1X, 1972BR1G, 1972DE03, 1972FR09, 1972GR1K, 1972GR42, 1972KR11, 1972KR1D, 1972LE1L, 1972SI24, 1972VA40, 1972VE01, 1973AB1A, 1973AR1C, 1973BU12, 1973CA16, 1973DO1F, 1973EN1E, 1973ER1C, 1973ER10, 1973FE13, 1973FO1F, 1973GR36, 1973HA57, 1973KO26, 1973KU1L, 1973LE1E, 1973LO1C, 1973PE05, 1973SA38, 1973SA30, 1973VA01, 1974AB05, 1974AD1C, 1974AR04, 1974BA1Z, 1974DU02, 1974DZ03, 1974JA24, 1974KA23, 1974MU13, 1974SI03, 1974VA1N, 1974ZA01).
For E(6Li) = 1.2 to 2.8 MeV, population ratios of 7Be*(0.43), 7Li*(0.48) and 10B*(0.72) (reactions (c), (e) and (f)) 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 (0°) (reaction (d)) shows two broad peaks at E(6Li) = 4 and 9 MeV (1967CA1D: prelim. results; E(6Li) = 2 to 14.5 MeV) while (1970FR06: E(6Li) = 4 to 24 MeV) report a broad peak at E(6Li) ≈ 10 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 quasi-molecular 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 (1971GA1N, 1971GA21, 1972GA32). See also (1971WY01), (1968AJ02) for the earlier work, 8Be and 10B in (1974AJ01) and 11B and 11C for reactions (a) and (b).
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). See also (1973GO01). 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: θc.m. = 88°). See also 6Li in (1974AJ01). For reaction (a) see 6He in (1974AJ01).
At E(7Li) = 2.6 MeV, population of 12C*(4.44, 15.11) is reported (1962BE24).
(1970BL09) had reported the observation of a capture resonance at E(3He) = 1.74 MeV which subsequently decayed via 12C*(15.11) and which was assumed to correspond to the first Jπ = 0+; T = 2 state in 12C [Ex = 27.585 ± 0.005 MeV]. However, neither (1972HA63) nor (1972WA18) have been able to repeat this measurement: Γ3HeΓγ/Γ < 1.5 meV (1972WA18), < 2 meV (1972HA63). See also (1974HA1G). 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 12.10 (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).
Excitation functions for neutrons have been measured for E(3He) = 1.2 to 9.9 MeV for several neutron groups: see (1968AJ02) 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 (1965DI06, 1963DU12). The total cross section for 11C production rises monotonically for E(3He) = 0.60 to 1.15 MeV (1973SU07) and then shows a broad maximum, σ = 113 mb, at E(3He) = 4.3 MeV (1966HA21: E(3He) = 3.2 to 10 MeV). 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). See also (1970KR09) and 11C.
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) for a listing of the earlier references. The yields of ten proton groups have been determined for E(3He) = 0.50 to 1.10 MeV (θ = 110°): the yields increase monotonically (1971ST1H, 1973SU07). The excitation curves at higher energies show only a slow and smooth increase: see, e.g. (1960HI08). See also 11B. The excitation function for reaction (c) has been measured from threshold to E(3He) = 31 MeV (1974MO23).
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°). For reaction (a) see (1967CR04). See also 9B and 10B in (1974AJ01).
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). See also (1974BO38: E(3He) = 1.2 to 2.5 MeV). Polarization measurements are reported at E(3He) = 18 MeV (1972MC01) and 31.4 MeV (1971EN03). See also 9Be in (1974AJ01).
Excitation functions at θ = 140° (reaction (a)) do not show resonant behavior for E(3He) = 1.0 to 1.9 MeV (1970EH1A: α0, α1; unpublished work). For reaction (b) see 8Be in (1974AJ01) and (1972TA04). See also (1971OS05; theor.).
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 = 1.9 to 23 MeV: see (1968AJ02) for earlier references and (1969KL09: Eα = 1.75 and 1.96 MeV; n0), (1970VA23: Eα = 2.55 to 7.87 MeV (n0); 2.55 to 7.47 MeV (n1); 4.36 to 7.47 MeV (n2)), (1972OB01: 3.21 to 6.44 MeV (n0, n1, n2); 6.24 and 6.44 MeV (n3)) and (1968VE06: 6.79, 7.96, 8.91, 9.92 MeV; n0, n1, n2).
The mean life of 12C*(4.4) [Jπ = 2+] is 57+23-17 fsec, Γγ = (11.5+5-3.2) meV (1966WA10): see Table 12.9 (in PDF or PS). 12C*(7.7) decays predominantly into 8Be + α (see reactions 20 and 35), Jπ = 0+, Γπ/Γ = (6.9 ± 2.1) × 10-6 (1960AL04, 1972OB01).
See (1959AJ76, 1968AJ02) for surveys of the earlier work. See also 13C in (1976AJ04) and (1968LE24, 1969KL1C, 1969NO01, 1969ZI1A, 1970FO1C, 1970GE1A, 1972DA32, 1972DE10, 1973TY1A, 1973VI1C, 1973WE03) and (1968VA1E, 1969HO34; theor.).
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). Upper limits to the differential cross sections for γ0 and γ1 are 5 nb/sr and 50 nb/sr, respectively for Ed = 4.0 to 20.2 MeV (1971SH1E; prelim. results).
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). The 0° excitation function for ground state neutrons shows no structure for Ed = 3.2 to 9.0 MeV (1967DI01). The excitation function for the neutrons to 11C*(6.48) increases monotonically for Ed = 4.0 to 4.8 MeV (1972TH14). 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 2.90 MeV (1968BR26: n0) and 2.4 to 4.0 MeV (1972ME06: n0, n1, n2+3). The transitions to 11C*(0, 4.32 + 4.80) appear to involve a direct reaction mechanism (1972ME06). See also (1969DI08) and 11C.
Absolute yields have been measured for various proton groups for Ed = 0.14 to 12 MeV: see (1968AJ02) and (1972AR31: Ed = 0.7 to 2.5 MeV; p0 → p3) and (1970BL09: Ed = 2.605 to 2.960 MeV; p0 → p3). See also (1970PO03). 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). See also (1972AH1A). For a study of the branching ratio n0/p0 see reaction 14 (1973BR24).
Polarization measurements have been carried out recently for Ed = 1.15, 1.40 and 1.85 MeV (1969DI08; p0), 10 MeV (1969CU10: p0) and 10 and 12 MeV (1970FI07, 1972FI1E: p0) and 13.6 MeV (1967GO27: p0). For earlier polarization studies [Ed = 6.9 to 21 MeV] see (1968AJ02). See also (1967GO27, 1967SA06), (1970DE35, 1973CO18; theor.) and 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 = 0+; T = 1 and Jπ = 1+; T = 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 = 9, 10 and 11 MeV (1972FI1E, 1973FI1C) and at 15 MeV (1974BU06). See also 10B in (1974AJ01).
Excitation functions have been measured for the α0 and α1 groups for Ed = 0.4 to 3.3 MeV: see (1968AJ02) for earlier references and (1968FR07: 0.5 to 2.0 MeV), (1968CO31: 0.8 to 2.5 MeV) and (1970BL09: 2.605 to 2.960 MeV). The α0 yield has also been measured for Eα = 4 to 12 MeV by (1971RE1D) and the yields to 8Be*(16.6, 16.9) have been determined for Ed = 2.856 to 2.906 MeV by (1972AH1A; in 2 keV steps; unpublished). A number of broad maxima are observed in the excitation curves above Ed = 1 MeV. The α0 yield shows such a maximum at Ed = 1 MeV which (1968FR07) attribute to an s-wave resonance corresponding to a state with Ex ≈ 26.0 MeV, Γ ≈ 0.5 MeV. No evidence for the T = 2 state reported in reaction 4 was found in the α0 and α1 yield curves taken in 2 keV steps for 27.35 < Ex < 27.65 MeV (1970BL09). See also (1972AH1A). The relative populations of 8Be*(17.6, 18.1) have been determined for Ed = 4 to 12 MeV (1970CA12): see 8Be, reaction 38 (1974AJ01). For reaction (b) see (1968AS01, 1973RO28) and 8Be in (1974AJ01). See also (1967LE1C, 1967NA11) and (1970KO01, 1970KO27, 1971LA25; theor.).
This reaction has been studied for Ed = 8 to 13.5 MeV (1964GE10).
Proton groups observed by (1958MO99, 1959AL96, 1962BR10) are displayed in Table 12.11 (in PDF or PS). Angular distributions of many of these groups have been measured for E(3He) = 1.4 to 14 MeV: see (1968AJ02) for the earlier references and (1970BE1F).
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, 13.3), 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 12.11 (in PDF or PS), and (1968AJ02). 12C*(12.7) decays also by γ-emission: the cascade via 12C*(4.4) is 15 ± 4%, the crossover transition is 85 ± 4% (1972AL03); Γγ/Γα = 2.5 ± 1% (1958MO99, 1959AL96). 12C*(15.11) [Jπ = 1+; T = 1] decays by γ-emission to 12C*(0, 4.4, 7.7, (10.3), 12.7): see Table 12.9 (in PDF or PS) (1972AL03). It is suggested by (1972AL03) that an isospin-forbidden α-decay branch from 12C*(15.11) to 8Be*(2.9), which had been reported with an intensity of (1.2 ± 0.7)% in reaction 67, does not exist: the problem might have been an inaccurate determination of the intensity of the γ-branch to 12C*(12.7) by (1970RE09): see, however, (1974BA42) in reaction 67.
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).
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).
At Eα = 21.2, 23.0 and 25.0 MeV angular distributions of the deuterons to 12C*(0, 4.4) have been measured (1967AL16). The (dγ4.4) angular correlations have been measured for Eα = 19 to 25 MeV (1972EL09). See also (1967SP09, 1973HA1Y, 1973SP1D), (1971BU1K, 1973ZE03; theor.) and 14N in (1976AJ04).
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 also (1969CO1D, 1970GI05).
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). See also (1968OK06).
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. 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). 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 (1970BR1J, 1972BR26) for γ0, γ1 and γ3 [to 12C*(0, 4.4, 9.6)]: disagreement is reported with the cross section values reported by (1964AL20). The γ2 yield to 12C*(7.7) exhibits a peak at Ep ≈ 14.3 MeV with a cross section ≈ 2.3% that of γ0. The γ3 yield shows two large asymmetric peaks at Ep = 12.5 and 13.8 MeV with Γ ≈ 0.7 and 2.5 MeV, respectively, as well as a weaker structure near Ep = 9.8 MeV (1971SN1A: Ep = 6 to 18 MeV; abstracts). (1969KE02: Ep = 13 to 21 MeV) report a broad peak in the γ0 cross section at Ep = 14.8 MeV [Ex = 29.5 MeV]. The previously reported resonance in γ0 at Ep = 20.1 MeV [see (1968AJ02)] does not exist: see (1969KE02, 1972BR26). No evidence is seen in this reaction for the Jπ = 0+; T = 2 state reported in reactions 4 and 12 (1974HA1G: search for γ12.5 + γ15.1, that is (0+; 2) → (1+; 1) → (0+; 0)). Work on other resonances is discussed below. See also the reviews by (1968BR1D, 1968SC1B, 1972HA1Y, 1973GL1C, 1973HA1Q, 1973SU1E, 1974HA1N), (1972CA1H) and (1969MA22, 1970GO41, 1973BA05, 1973HA1X, 1973SU03; theor.).
(b) Excitation functions for α0 have been measured recently for 7.50 < Ep < 18.9 MeV: no marked structure is observed above Ex = 28 MeV (1972TH1C: Ph.D. thesis; (1969TH1B, 1971TH1F); abstracts). See also 8Be in (1974AJ01) and (1968CH01, 1971GU23).
(c) This reaction has been studied for Ep = 0.15 to 9.5 MeV. It proceeds predominantly by sequential two-body decay via 8Be*(0, 2.9): see 8Be in (1974AJ01) and (1968CH01, 1968GI03, 1969QU01, 1970CO03, 1971KO22, 1971YA13, 1972CH35, 1972DZ10, 1972HU04, 1972MI1J, 1972TR07, 1972VO01, 1973PR1C). See also (1969PH1B), (1967CO29, 1967EN1A, 1967FL12, 1968LA1C, 1969LA1B, 1970PA10), (1969GO13, 1969SA1B, 1970GI1C, 1970GO1J, 1970GO33, 1970GO49, 1970KO01, 1970KO1K, 1970KO27, 1970MC25, 1970MC1T, 1970SC01, 1971GO20, 1971LA25, 1972GO1N, 1972KO1J, 1973GO35, 1973KO11, 1973KO38; theor.) and (1974LI1M; applied).
The parameters of the observed resonances are displayed in Table 12.12 (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): 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). See also Table 12.9 (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 ≈ 0.01 W.u., suggesting T = 1 (1957DE11, 1965SE06). (1962BL10) report a γ branch to 12C*(12.71) (≈ 6% of the intensity of the γ1 transition). Such a branch may also be present for 12C*(17.23). See also (1973PR1C).
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 12.12 (in PDF or PS)) is favored by elastic scattering data (1965SE06).
Ep = 2.0 MeV [12C*(17.76)]. 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*(18.36)]. 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).
Levels 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 from this reaction and reduced widths obtained from the (d, p) and (d, n) reactions: see Table 12.13 (in PDF or PS) (1971MO14, 1974AN19).
Excitation functions have been reported for Ep = 2.6 to 11.5 MeV. They are characterized by numerous peaks: see Table 12.14 (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). The strength of the pronounced peak at Ep = 6.03 MeV (Ex = 21.49) appears to demand J ≥ 4 (1961LE11).
The polarization transfer coefficient has been measured for Ep = 7 to 15 MeV: the strong influence of resonances is apparent (1974LI1J). See also (1974MA07; theor.). Polarization measurements have been carried out for Ep = 7 to 11 MeV (1965WA04) and at 24.5 MeV (1972MO41). See also (1973BA05; theor.), 11C and (1968AJ02).
A pronounced anomaly in the elastic scattering is observed near Ep = 0.67 MeV at all angles; the level is therefore formed by s-waves. The 0.3 to 1.0 MeV results are well accounted for by two resonances: Ep = 0.67 MeV, s-wave, Jπ = 2-, Γ = 0.33 MeV, Γp/Γ = 0.5, and Ep = 1.4 MeV, Jπ = 1- (1957DE11). Higher energy structure in the yields of reactions (a) and (b) are displayed in Table 12.14 (in PDF or PS) (1955BA22, 1965SE06, 1971SA1H). Excitation functions for p0 and p1 have been measured for Ep = 7.5 to 21.5 MeV: no pronounced structure is observed above Ex = 28 MeV (1972TH1C: Ph.D. thesis; (1969TH1B, 1971TH1F); abstracts).
Polarization measurements have been reported at Ep = 1.9 to 3.0 MeV (1974DE45: p0), 3.5 to 10.5 MeV (1971SA1H; prelim. report; p0, p1), 30.3 MeV (1969KA15, 1971LO05; p0, p1, p2) and 155 MeV (1968GE04; p0, p1, p2, p4). See also (1965HU10, 1968RI1J, 1972RE06) and (1969WA11, 1971BL1E; theor.). For reaction (c) see (1971RA26). See also 11B and 10Be in (1974AJ01).
See 10B in (1974AJ01).
Reported neutron groups are displayed in Table 12.15 (in PDF or PS). Angular distributions have been reported for many energies in the range 0.5 < Ed < 11.8 MeV: see (1968AJ02) for a listing of the earlier references and (1970BU15: 5.5 MeV; n0, n1), (1967FU07: 6 MeV; see Table 12.15 (in PDF or PS)), (1974AN19: 6 MeV; n to 12C*(15.1, 16.1); see Table 12.13 (in PDF or PS)), (1971MU18: 11.8 MeV; see Table 12.15 (in PDF or PS)). See (1971MU18) for a discussion of the problems involved in comparing spectroscopic factors obtained in this reaction and in the (3He, d) reaction [reaction 30].
Angular correlations of neutrons and γ-rays have been studied at many energies: see (1968AJ02) for the earlier references and (1968TE03: 1.6 to 3.3 MeV for γ4.4; 2.9 and 3.3 MeV for γ15.1) and (1972TH14: 4.0 to 4.8 MeV; γ4.4, γ15.1).
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).
Observed deuteron groups are displayed in Table 12.15 (in PDF or PS). Angular distributions have been measured at E(3He) = 5.1 to 44 MeV: see (1968AJ02) for the earlier references and (1969MI15: E(3He) = 10, 12 and 18 MeV), (1968BO26: 11 MeV), (1971RE03: 44 MeV). 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. The upper limit to 12C*(12.7) is ≈ 5% (1974AD1D).
Angular distributions have been measured at Eα = 15.1, 18.3 and 24.9 MeV (1972VA34: t0; and t1 at 24.9 MeV), 27 MeV (1969TE1B: t0, t1; unpublished) and 46 MeV (1969FO1C: t0 → t3 and t to 12C*(12.7); abstracts). See also (1968AJ02). The (t1, γ) angular correlations have been measured for Eα = 21.2 to 25.0 MeV (1972EL09). See also (1973ZE03; 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). See also (1973DE35; theor.).
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 (1968OK06), (1969BR1D, 1972MO1E) and (1968VA1D, 1969KA1G, 1970AN1D, 1970SC1G, 1972BO21, 1973DE1W, 1973DE35, 1973OS03, 1974OS1A; theor.).
The decay is mainly to 12Cg.s.; branching ratios to 12C*(4.4, 7.7, 10.3) are shown in Table 12.16 (in PDF or PS). All the observed transitions are allowed. The half-life is 20.41 ± 0.06 msec [see 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+ (1957CO59). (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 [see Table 12.9 (in PDF or PS)] 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).
A search for transitions to 12C*(12.7) has been unsuccessful (1967AL03). See also reaction 63. For asymmetry measurements see (1967PF02, 1973ST1P, 1974PO05). See also 12C, reaction 28 in (1968AJ02), and (1971MI06, 1973CH16, 1973MIYZ, 1974PO05).
See also (1974AL11), (1968DA1J) and (1969BL1D, 1969CH1A, 1969CH1F, 1969MO1F, 1970ST04, 1971BL06, 1971KI04, 1971KI11, 1971LA21, 1971LI1F, 1971LI1H, 1971WI18, 1971WI1C, 1972AR04, 1972EM02, 1972OC01, 1972WI28, 1972WI1C, 1973BO09, 1973EM1B, 1973HA49, 1973KU1D, 1973KU1N, 1973TO14, 1973WI11, 1973YO04, 1974BO18, 1974HO1D, 1974WI1L, 1975GR03; 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). The partial widths are displayed in Table 12.9 (in PDF or PS). The scattering angular distribution indicates dipole radiation (1959GA09), the azimuthal distribution of scattered polarized radiation indicates M1 (1960JA01) and the large Γγ indicates T = 1. The branching ratio for the cascade decay via 12C*(4.4) is 3.6 ± 0.7% (1970AH02). Elastic scattering to 12C*(4.4, 16.1, 17.2) has also been observed. See also (1968AJ02) and Table 12.20 (in PDF or PS).
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 reaction 37, (1969MO1H, 1971ME1B) and (1968SI1A; theor.).
The total absorption, mainly (γ, n) + (γ, p), is dominated by the giant resonance peak at 23.2 MeV, Γ = 3.2 MeV [σmax = 19.8 mb (1965WY02)] and by a smaller structure at 25.6 MeV, Γ ≈ 2 MeV (σmax ≈ 8 mb): see (1968AJ02) [Tables 12.16 (in PDF or PS), 12.17 (in PDF or PS)] for a detailed listing of the earlier references and results, and see (1973AH1A, 1974BE2B). See also (1967DO1A, 1969BE92). Total absorption cross sections have also been measured at Eγ = 84 to 662 keV by (1968RA1D), at 7.28 and 7.65 MeV by (1969MO1H), at 10 to 140 MeV by (1970AH02, 1972AH1B, 1973AH1A) and at 250 to 1000 MeV by (1972MI1K, 1974HO15). See also Table 12.16 (in PDF or PS) in (1968AJ02).
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 (1968AJ02). The giant resonance peak is rather flat-topped with several small fine structure bumps across the top (E.G. Fuller, private communication): see (1966CO09, 1966FU02, 1966LO04, 1971IS09, 1972VA32, 1973BE2F, 1973IS1A, 1974BE2B). 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. [See the reviews by (1970HA1F, 1973HA1Q).] 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, 1970JU1C, 1973JU1C). The fraction of transitions to the ground state and to excited states of 11C has been measured at Ebs = 24.5 to 42 MeV: see 11C (1970ME17), reaction 38 and the discussion in (1973DI1C). For polarization measurements see (1973NA1K) and (1968AJ02). For a listing of recent cross section measurements see Table 12.17 (in PDF or PS).
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).
See also (1967AN11, 1969DE12, 1971JO1E, 1973MO1G, 1973VA12), (1972BU1J, 1973CO1N, 1973HA1Q) and (1968PA1H, 1969ER1A, 1969GA1J, 1969GO1D, 1969MA22, 1969UB01, 1970GO41, 1970MU1D, 1971AN08, 1971BA97, 1971BI01, 1971WA27, 1972BI11, 1973BA05, 1973BE1W, 1973BI1K, 1973MA1T, 1973MS01, 1973MS02, 1973SR1B, 1973SU03, 1973WE1U, 1974CA1R, 1974FI03, 1974GI1A; theor.). For applied work see (1973AL1G).
The photo-proton cross section exhibits two broad peaks, the giant resonance peak at 22.4 MeV, Γ = 3.2 MeV, σmax = 13 mb [see Table 12.19 (in PDF or PS) in (1968AJ02)], and a second broad peak at 25.1 MeV, in addition to some fine structure. In contrast with the giant resonance peak in the (γ, n) cross section, the (γ, p) cross section shows a sharp 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). The (γ, p) results of (1968FR12, 1968FR14, 1969CA22) are in good agreement with those of (1964AL20) for the inverse reaction, 11B(p, γ0)12C [see reaction 25], when the population of 11B*(4.4, 5.0) is taken into account: the required cross sections for the (γ, p2) and (γ, p3) processes peak at 1.5 mb at 29 and 30 MeV, respectively (1973DI1C, 1974DI17). The fraction of transitions to the ground and excited states of 11B at several energies in the range Ebs = 24.5 to 42 MeV has been measured by (1970ME17): most of the transitions are to 11Bg.s. and the excited state transitions appear to originate from localized Ex regions. See 11B and the discussions in (1970HA1F, 1973DI1C). Proton spectra and angular distributions have also been measured at Ebs = 50 to 80 MeV (1968MA32, 1969MA23), 98.5 MeV (1968MA19) and 80, 120, 285 and 1140 MeV (1970AN34). The ratio of deuterons to protons has been determined at 1140 MeV by (1972AN1M). For polarization measurements see (1970TO09). See also (1968AJ02) for the earlier measurements and reaction 44.
See also (1970WO1E, 1971AN04, 1971EG03, 1971EG02, 1971GO32, 1971IR1C, 1972TO22, 1973DO13, 1974BO47, 1974DO08, 1974DO07), (1972BU1J, 1973CO1N, 1973HA1Q) and (1969GA1J, 1969GO1D, 1969MA22, 1969UB01, 1970GO41, 1970MU1D, 1971BA97, 1971BI01, 1971GI1D, 1972AK02, 1972BI11, 1972WE1G, 1973BA05, 1973BE1W, 1973DE1Y, 1973LA1M, 1973MS01, 1973MS02, 1974SE02; 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). The high apparent threshold for reaction (a) is thought to reflect the presence of continuum states of 10B with a high parentage in 12C (1964SH1B). 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). See also (1969AN1F, 1969AN10, 1971AN04, 1971AN15, 1972AN09, 1972AN1M) for excitation functions to 1400 MeV, and (1968AJ02). For reaction (b) see (1968TA10, 1969TA11) and (1973KO1H; theor.).
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).
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. It is assumed to be the dipole state with a 5p - 5h character (Jπ = 0+) based on 12C*(7.66) considered to be relatively pure 4p - 4h (1969OW01). For work on the γ-induced spallation of 12C see (1968TA10, 1969TA11). See also (1968DI1B, 1969DI18, 1971DI1F) and (1969ER1A; theor.). For older work on these reactions see (1968AJ02).
The nuclear charge radius of 12C, Rrms = 2.462 ± 0.022 fm (1973FE13). Other values include Rrms = 2.445 ± 0.015 fm (Fermi model), 2.453 ± 0.008 fm (shell model) (1972JA10). See also (1969BE21, 1970BR1C, 1970SI08, 1971BE25, 1973EN1E, 1973KL12, 1973TH1B) and (1968AJ02). Elastic scattering has been studied up to 4 GeV: see (1968AJ02) for the earlier references and (1972JA10: Ee = 20 → 80 MeV), (1973KL12: Ee = 374.6 MeV), (1970SI08: Ee = 374.5 and 747.4 MeV) and (1971ST10: Ee = 1 to 4 GeV).
12C states observed in the inelastic scattering are displayed in Table 12.18 (in PDF or PS) (1963BO36, 1965BI1B, 1967CR01, 1968BE1H, 1968DO08, 1968ST20, 1969GU05, 1969TO01, 1970AN1C, 1970LI02, 1970ST10, 1970TO13, 1971BE51, 1971NA14, 1972SP1C, 1973CH16, 1974CE01). See also (1968PR01, 1969VA10). The variation of the form factor F(q2) with momentum transfer yields unambiguous assignments of Jπ = 2+, 0+ and 3-, respectively for 12C*(4.4, 7.7, 9.6) (1960BA38, 1964CR11, 1967HA1F). Form factors for 12C*(0, 4.4, 14.1) have been measured by (1971NA14). The isospin mixing between 12C*(12.71) and (15.11) [both Jπ = 1+; T = 0 and 1, respectively] has been measured by (1974CE01): β = 0.19 ± 0.01 or 0.05 ± 0.01.
Inelastic scattering of the giant resonance has been studied by many groups: see (1968AJ02) for the earlier work and Table 12.18 (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). See also (1969TO10). 12C*(19.3) may be the expected giant magnetic quadrupole state, Jπ = 2-: see (1968AJ02) and (1968BE1H, 1968DR01). See also (1970GR27; theor.).
(1974OB01) has measured the most probable energy loss for Ee = 50 and 100 MeV. See also (1968DE25, 1969CA1C, 1970AN1G, 1970DE04, 1971TI03, 1973ME1K), (1968GO1J, 1972THZF, 1973BI1A, 1973TH1B), reaction 44 and (1968AN1B, 1968BO1J, 1968CI1C, 1968FR1E, 1968HE1C, 1968HO1B, 1968KE10, 1968MA1N, 1968RA1B, 1969CH01, 1969CH1A, 1969CI1A, 1969DE14, 1969DO1D, 1969FU1F, 1969HE1F, 1969KA1H, 1969KU1C, 1969UB01, 1969VI02, 1970CH1H, 1970CH1J, 1970CI1B, 1970DO1F, 1970DO1G, 1970DO1H, 1970DO1A, 1970FR1E, 1970GO41, 1970GU12, 1970HI1C, 1970JA08, 1970LI18, 1970LI1P, 1970MC1D, 1970ON1B, 1970SA1B, 1970SP1C, 1971CI03, 1971DE1T, 1971DU06, 1971FR13, 1971MO1Q, 1971TA13, 1972AB19, 1972AN03, 1972AN15, 1972BE1X, 1972BO01, 1972EL11, 1972FR06, 1972GU25, 1972LE45, 1972OC01, 1972PA32, 1972ST35, 1972SU01, 1972UB01, 1973AL14, 1973BA05, 1973BO1Q, 1973DO1H, 1973FO1G, 1973FO1F, 1973GA19, 1973KU1N, 1973MA07, 1973MU04, 1973RI1A, 1973ROYN, 1973SI13, 1973SI1P, 1973SU03, 1973TA1F, 1974AB05, 1974BA1Z, 1974DZ06, 1974DZ05, 1974FR12, 1974IN05, 1974SI03; 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). A study of e' - p coincidences for Ee = 550 - 600 MeV reveals peaks corresponding to ejection of 1p and 1s protons: the results are consistent with observations in (p, 2p) (1964AM1C, 1967AM03). At Ee = 497 MeV, the proton spectrum is dominated by an l = 1 transition to 11Bg.s. (1974BE12). See also (1971BU26). The data obtained by (1974BE12) do not satisfy the sum rule of (1972KO01). The quasi-elastic scattering cross section has also been measured at Ee = 199.5 MeV (1969GU05), 500 MeV (1971MO06, 1974WH05) [the Fermi momentum is 221 ± 5 MeV/c (1971MO06)], 1 to 4 GeV (1971ST10) and 2.5 and 2.7 GeV (1974HE20, 1974KO21). See also (1967AM1A, 1968BO46, 1968DE25, 1969BE1L, 1969DE20, 1970DE04, 1970HI1F, 1970VY01, 1970WO1E, 1971EG03, 1971EG02, 1971SH09, 1972BE1U, 1972VL1A, 1973HE1H, 1974BA70, 1974SI1G) and (1967AM1C, 1972RA1E).
Absolute cross sections for reaction (b) have been measured for Ee = 20 to 30 MeV, using both electrons and positrons (1972KU27). See also (1973MO1G, 1973VO09). For reaction (c) see (1970EN1A). For reactions (d) and (e) see (1969TI04, 1970TI03, 1971TI03, 1971ST10, 1973HE1H) and the "Pion capture and pion reactions" section here. See also (1968BO1J, 1968BO1D, 1968CI1B, 1968DE1F, 1968MA1M, 1968WA1D, 1969DR05, 1969MO1G, 1969ST1E, 1969VY1A, 1969WA1E, 1970CI1C, 1970EP1A, 1970PA1H, 1970SI23, 1971BO1M, 1971CI1A, 1971PA42, 1971SH18, 1972AM1C, 1972AN03, 1972RA20, 1972RA18, 1972WE14, 1973BA2M, 1973BA71, 1973CI1A, 1973HI03, 1973JO1H, 1973SH02, 1974HA14, 1974KN1C, 1974ME24; theor.).
Angular distributions of the elastic scattering and for the inelastic scattering to 12C*(4.4, 9.6, 15.0) have been measured at Eπ- = 120 to 280 MeV (1970BI1A). [Not all groups were measured at the seven energies in the above interval. 12C*(9.6) represents the group of levels with 9.6 ≤ Ex ≤ 10.8 and 12C*(15.0) those with 15.1 ≤ Ex ≤ 17.2 (1970BI1A).] 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+. The population of 12C*(15.11) was not observed in either reaction (1970HI10). The involvement of 12C*(4.4) in reaction (c) has been studied by (1973AS1A). See also the "GENERAL" section here, (1971TH05, 1975PI1E) and (1971RO14, 1974JA1F, 1974NI08; theor.).
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). Angular correlations of (n1, γ4.4) have been studied at En = 13.9 MeV (1973DE45) and 15.0 MeV (1971SP01), and at 14 - 14.7 MeV [see (1968AJ02)]. The spin-flip probability for the transition to 12C*(4.4) has been studied at En = 7.48 MeV (1971MC1K, 1972MC20) and at 15.0 and 16.9 MeV (1973TH08, 1974ME29). The shape of the angular distribution of the probability at En = 7.48 MeV is similar to that measured by (1964SC07) in the (p, p') reaction at Ep = 10 MeV (1972MC20); while that at En = 16.9 MeV is similar to that measured by (1969KO07) at Ep = 20 MeV (1974ME29).
At En = 14.4 MeV reaction (b) involves 12C*(9.6, 10.8, 11.8, 12.7). The decay of 12C*(11.8) leads to an assignment of Jπ = 1- (1964BR25, 1971DO1K, 1975AN01, 1975AN02). [See, however, Table 12.8 (in PDF or PS)]. See also (1966MO05, 1968BE1J).
See also 13C in (1976AJ04), (1968BR05, 1968KO1A, 1969PE1C, 1969RO1F, 1970BR1K, 1970MA1J, 1972DE31, 1974DR1C), (1968CA1A, 1968CH35, 1968TI1B, 1969AL1C, 1969DU1B, 1969OL03, 1970CA13, 1970SH14, 1971CH01, 1971MI07, 1972IK01, 1972JO11, 1972MO45, 1974CH1X; theor.) and (1969TR1A; astrophys. problems).
Angular distributions of elastically and inelastically scattered protons have been measured at many energies up to Ep = 1040 MeV: see Table 12.22 (in PDF or PS) in (1968AJ02) for the earlier work and Table 12.20 (in PDF or PS) here. Angular distributions at Ep = 20 MeV (1963DI16, 1970BL03) and 46 MeV (1967PE05) show that a large quadrupole deformation exists: β2 = -0.72 (1972DE13) and 0.6 (1967SA13), respectively.
Table 12.21 (in PDF or PS) shows the information on excited states of 12C. The angular distribution for 12C*(7.7) is best described by double quadrupole excitation via 12C*(4.4). 12C*(14.1) is identified as the 4+ rotational state (1967SA13). The values Ex = 7656.2 ± 2.1 keV (1971AU16), 7655.9 ± 2.5 keV (1971ST22) obtained for the 0+ second excited state of 12C lead to a substantial change in the reaction rate for helium-burning nucleosynthesis: see (1971AU16).
The in-plane and spin-flip pγ4.4 angular correlations have been measured at 20 MeV. The substate cross sections were determined: these show a more pronounced structure than does the total inelastic cross section to 12C*(4.4). The M = 0 cross section is the most diffraction like. Agreement with the compound nucleus DWBA predictions is poor (1972TE01). The spin-flip probability in the scattering to 12C*(4.4) has been studied at Ep = 8.00 to 8.30 MeV (1972BE15), 12 to 14 MeV (1970KO15), 12, 13, 14, 15 and 20 MeV (1969KO07), 15.9 and 17.35 MeV (1971WI16) and 26.2 and 40 MeV (1969KO13). See also (1973SA1N). (1972BE15) find that the interference between the resonant and the background spin-flip is large: see 13N in (1976AJ04). At Ep = 26.2 and 40 MeV the observed spin-flip is almost entirely accounted for by distortions in the entrance and exit elastic channels, due to the spin-orbit term in the optical model potential (1969KO13).
For polarization measurements see (1970LI19, 1975GL1C) and 13N in (1976AJ04). See also (1971GA42, 1973TH1A, 1974AL1G, 1974BR1J, 1974DA1Q, 1974GA30, 1974OB1C, 1975PI1E), (1964KA1A, 1967LE13, 1968BA1K, 1968CH35, 1968GL1A, 1968KO26, 1968LE1D, 1968LI1B, 1968NE1B, 1968TA1D, 1968TA1E, 1968TI1B, 1969BA06, 1969BY1A, 1969HA07, 1969KO1H, 1969LE03, 1969MA1G, 1969NE1A, 1969OL03, 1969PE1E, 1969TA1D, 1969TI02, 1969WA11, 1970BA1F, 1970CA13, 1970CZ1A, 1970DA17, 1970GU15, 1970HA1J, 1970KO1L, 1970KR1E, 1970KU1C, 1970SA06, 1970SH01, 1970SH14, 1971AH03, 1971CH01, 1971FR1L, 1971HA31, 1971IN05, 1971JA16, 1971LE01, 1971MI07, 1971MO18, 1971RA36, 1971SH18, 1971SI11, 1971SI37, 1972AN12, 1972AU1A, 1972BA2E, 1972JO11, 1972IK01, 1972SI19, 1972SO03, 1972ST35, 1973AL14, 1973AU05, 1973DO10, 1973FR08, 1973GE1E, 1973KA04, 1973MA2B, 1973MI19, 1973SI37, 1973VA18, 1974AL1H, 1974BE22, 1974BR06, 1974IN04, 1974IN06, 1974IN07, 1974JA1F, 1974KU20, 1974SC1K, 1974ST02, 1973TE1B; theor.) and (1969TR1A; astrophys. questions).
At Ep = 56.5 MeV, 12C*(20.3 ± 0.5) is excited and then decays to 11Bg.s. (1969EP01). At Ep = 385 MeV and estimate of the momentum distribution of the protons bound in 12C has been obtained. The results are consistent with a model in which the nuclear core is essentially a spectator. Distortion effects are mainly of an absorptive nature (1969JA05). At Ep = 1.0 GeV, the process is essentially quasifree (1970SI01, 1972CO11). See also (1971PA1H). Small angle multiple scattering of 600 MeV protons has been measured by (1972HU12). The angular correlation to 11B(0) has been measured at Ep = 49.5 MeV by (1971HA61).
See also (1968AJ02) for earlier references, 11B, (1968PE1A, 1971LA16, 1971LO25), (1969JA1F, 1969VO1E, 1972RA1E) and (1968DE1G, 1968JA1E, 1969GU1G, 1969JA1D, 1969KO1J, 1969MC13, 1970FL1B, 1970KR1E, 1971JA11, 1971JA16, 1971MC26, 1971SH18, 1971WI15, 1971YO1E, 1972AB1G, 1972CH1L, 1972JA1C, 1972PE04, 1972PI11, 1972ST29, 1972WI16, 1973ER19, 1973FR09, 1973GU1D, 1973JA01, 1973JO1H, 1973SH02, 1974BH1B, 1974PI01; theor.).
For reaction (b) see (1968PA05: Ep = 450 MeV). See also (1971TH05: p-bar, p-bar n), (1970TH1F) and (1972AB1G; theor.). For reaction (c) see (1970BA1T, 1971AZ01, 1972AZ03, 1972BO17, 1973KO1M) and (1968RO1F, 1974ZH01; theor.).
At Ep = 56.5 MeV, reaction (d) proceeds primarily by sequential α-decay: initially 12C*(19.7 ± 0.5, 21.1 ± 0.3, 22.2 ± 0.5 and 26.3 ± 0.5 MeV) are formed. The states, which therefore must 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 = 160 MeV, knock-out, sequential decay and spallation processes are observed (1970GO12). See also (1969HO1K, 1971GA1J, 1972MA62, 1972YA1B, 1973HO1R, 1973TH1A) and 8Be and 9B in (1974AJ01). For spallation studies see (1968KO1E, 1969DA1D, 1969ED01, 1969KO1G) and 13N in (1976AJ04). See also (1968ED1A). For pion production see (1970DO04), (1971IN1A, 1971RE12, 1972KE1F, 1973DI1G, 1974MI11; theor.), the "Pion capture and pion reactions" section here and 13C in (1976AJ04).
The angular distribution of elastically and inelastically scattered deuterons has been studied at many energies to Ed = 650 MeV: see (1968AJ02) for the older references and Table 12.22 (in PDF or PS) here. DWBA analysis of the distributions at Ed = 80 MeV leads to βl = 0.47 ± 0.05 and 0.35 ± 0.06 for 12C*(4.4, 9.6), respectively (1971DU09). Ex of 12C*(4.4) is 4440.5 ± 1.1 keV: the average of this value and of the one determined in (p, p') (Table 12.21 (in PDF or PS)) gives 4439.5 ± 1.0 keV (1974JO14). The isospin mixing of 12C*(12.71, 15.11) [both Jπ = 1+; T = 0 and 1, respectively] has been measured for Ed = 27.2 and 28.0 MeV. The ratio of the cross sections for the population of the T = 1 and 0 states is (7.0 ± 1.2) x 10-3. [In a remeasurement of this quantity (1975LI1K) find ≈ (1.1 × 10-2). Angular distributions for the two states were obtained at Ed = 24.1, 26.2, 27.5 and 28.8 MeV (1975LI1K).] This leads to β2 = 0.011 ± 0.003 (1972BR27: see also reactions 66, 67, 76). For a study of the distribution of ionic charge when 12C recoils in elastic scattering at Ep = 10 MeV, see (1971WO10).
Reaction (b) has been studied, in a kinematically complete experiment, at Ed = 5.00 to 5.50, 9.20 and 9.85 MeV by (1970SA1K, 1973SA03). An increase in yield is observed for all spectra in the region of low relative proton-neutron energy where both rescattering and sequential decay leading to the 1S0 final state interaction are possible. Due to the probable superposition and interference of different reaction mechanisms, it is apparently not possible to evaluate how much spin singlet and spin triplet interaction is involved (1973SA03). See, however, (1973SH04). Studies of reaction (b) are also reported at Ed = 5.1 to 6.25 MeV (1973SH04), 5.4 and 6.0 MeV (1968BO02) and 5.5 to 6.5 MeV (1970VA1K, 1972VA10). See also 13C and 13N in (1976AJ04) and (1972GE1G).
See also 14N in (1976AJ04), (1968VA12, 1968VE11, 1968VE1C, 1969KO1B, 1969PH1B, 1971PU01, 1972HE1E) and (1968DU01, 1968LY1A, 1968ME1E, 1968NO1C, 1969OL03, 1969TA1D, 1969VE09, 1970EL16, 1970OH1C, 1971GR54, 1971KO42, 1971KO43, 1971SI24, 1972BE54, 1972DM01, 1972ST1J, 1973HE1J, 1974AS1D, 1974IA02, 1974IN07; theor.).
Angular distributions of elastically scattered tritons have been determined at Et = 1.0 to 1.75 MeV (1962GU01, 1969HE08), 1.11 to 3.40 MeV (1969ET01 and private communication), 1.75 and 2.10 MeV (1969SI12), 6.4, 6.8 and 7.2 MeV (1964PU01), 12 MeV (1965GL04, 1966GL1B), 16 and 20 MeV (1972KE02) and 20.04 MeV (1974JA25). See also (1968HO1C) and (1971KA04; theor.).
Angular distributions of 3He ions have been measured at many energies in the range E(3He) = 2 to 217 MeV: see reaction 43 in (1968AJ02) for the older measurements and Table 12.22 (in PDF or PS), here, for the newer ones. DWBA analyses seem to be inadequate: complete coupled channels analyses appear to be necessary to explain the data; see, e.g., (1972AS03, 1973SI11).
Angular distributions of the 3He groups to 12C*(15.11, 16.11, 16.58, 19.57) have been compared with those for the tritons to 12N*(0, 0.96, 1.19, 4.25) in the analogue reaction 12C(3He, t)12N: the correspondence is excellent and suggests strongly that these are T = 1 isobaric analogue states (1968BA1E, 1969BA06: E(3He) = 49.8 MeV). See also Tables 12.13 (in PDF or PS) and 12.23 (in PDF or PS), 12N and (1970AR05, 1974WI16). The (3He', γ1) reaction plane angular correlation has been measured at E(3He) = 17 MeV as a function of gamma-ray angle for 43 3He scattering angles. The spin-flip probability was also determined, and the quadrupole deformation was found to be β2 = -0.60 (1968AS03, 1972AS03). See also (1971PA1K, 1974YA10). For polarization measurements see 15O in (1976AJ04).
Angular distributions have been measured at many energies to Eα = 166 MeV: see Table 12.24 (in PDF or PS) in (1968AJ02) and Table 12.22 (in PDF or PS) here. Alpha-particle groups have been observed to many 12C states: see Tables 12.22 (in PDF or PS) and 12.23 (in PDF or PS) (1972FA07). Jπ assignments have also been suggested for 12C states with 9.6 ≤ Ex ≤ 39.3 MeV on the basis of their decay into 3 α-particles: see (1973JA02; Eα = 90 MeV). See also (1969BA06).
Angular correlation measurements (α1γ4.4) have been carried out at Eα = 10.2 to 10.5 MeV (1972KE18), 18.0 to 24.0 MeV (1968KL07), 19 MeV (1972AS03), 19.3 to 25.3 MeV (1972EL09), 22.75 MeV (1970HA15), 32.5 MeV (1972BU09) and 41 MeV (1971BA64): the relative population of magnetic substates has been studied by (1970HA15, 1972BU09). See also (1968AJ02). The quadrupole deformation, β2, is -0.29 ± 0.02 (1971SP08), 0.46 (1973SM03); β3 = 0.24 (1973SM03). See also (1971BE60, 1972EE1A).
Measurements of the radiative widths yield Γrad/Γ = (4.2 ± 0.2) × 10-4 [Γrad ≡ Γγ + Γe± is then 3.7 ± 1.2 meV] for 12C*(7.7) (1974CH03) and Γrad/Γ < 4.1 × 10-7 [Γrad < 14 meV] for 12C*(9.6) (1974CH32): see also Table 12.9 (in PDF or PS). The value for Γrad for 12C*(7.7) implies a 45% faster rate for the (ααα) astrophysical process (1974CH03). See also (1973HA1Y, 1974MA2C). For total cross sections for formation of various 12C states, see 16O in (1971AJ02, 1977AJ02) and (1973SP1D).
For polarization measurements, see 16O in (1977AJ02). See also (1967HA1G, 1968CA11, 1968ED1B, 1968GA1D, 1968RA1C, 1968SH1D, 1968SH1E, 1968TO1D, 1969BU1D, 1969PI02, 1971MU1H, 1971TA30, 1971TE10, 1972DM01, 1973AL14, 1973BR1K, 1973BU1G, 1973DM01, 1973KU08, 1973SI1M, 1974PI11, 1974GO1U, 1974HO19, 1974WA02; theor.) and (1969TR1A; astrophys. questions).
Reaction (b) at Eα = 25 MeV appears to involve 12C*(7.66, 9.64) (1969DO02, 1969DO03). See also (1974RU06). See (1968YA02, 1969PI1B, 1970KE1B, 1970EI05, 1970PI1D, 1973RU09, 1974DO1G) for other studies of the (α, 2α) reaction with Eα up to 700 MeV. See also 8Be in (1974AJ01), (1971GA1J) and (1968BA1H, 1970BU1C, 1970MI12, 1972AV04, 1972MI05; theor.).
The elastic scattering in reaction (a) has been studied at E(6Li) = 4.5 to 13 MeV (1972PO07), 20 MeV (1968BE1K, 1972WA31), 24.5 MeV (1968DA20), 28 MeV (1972BA52), 30 MeV (1971CH1P, 1971DA33), 34 and 36 MeV (1973SC26; also 12C*(4.4)) and 36.4 and 40 MeV (1974BI04). See also (1964OL1A). (1974BI04) have also 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. Two step processes are important in the excitation of 12C*(7.7, 14.1) (1974BI1H). See also (1971DA1J) and (1968NO1C, 1971OS02, 1974AS1D; theor.).
The elastic scattering in reaction (b) has been studied at E(7Li) = 4.5, 5.8, 9.0, 11.0 and 13.0 MeV (1972PO07), 15 and 21.1 MeV (1972WE08) and at 36 MeV (1973SC26). At 36 MeV the angular distributions corresponding to 12Cg.s. + 7Li*0.48, 12C*4.4 + 7Lig.s. and 12C*4.4 + 7Li*0.48 have also been studied (1973SC26).
Elastic scattering angular distributions have been obtained at E(12C) = 12, 15, 18 and 21 MeV (1970BA49).
Angular distributions have been measured for reaction (a) at E(10B) = 18 MeV (1968VO1A, 1969VO10: to g.s.) and 100 MeV (1973BI1J, 1974BI1E: to 12C*(0, 4.4, 7.7, 9.6, 10.8, 11.8, 12.7, 13.4, 14.1, 14.8). Two-step processes appear to be involved in the excitation of 12C*(7.7, 14.1) (1974BI1E). See also (1974AS1D; theor.).
Angular distributions for reaction (b) have been studied at E(12C) = 15, 17, 20 and 24 MeV (1974BO15: to g.s.) and 87 MeV (1971LI11: to g.s.), and at E(11B) = 28 MeV (1968VO1A, 1969VO07, 1969VO10: to g.s., 4.4; and to several 11B states). A consistent description of the elastic data at E(12C) = 15 to 24 MeV is obtained by including the elastic transfer of a 1p1/2 hole (1974BO15). See also (1972SC1Q) and (1970AN1D, 1973DE35; theor.).
Angular distributions have been measured at E(12C) = 18.8 to 37.6 MeV (1973EM03: g.s. + g.s., g.s. + 4.4, 4.4 + 4.4), 40 to 60 MeV (1973WI09: g.s. + g.s., g.s. + 4.4, 4.4 + 4.4), 70 MeV (1971KO11: g.s.) and at 87 MeV (1971LI11: g.s.). At E(12C) = 114 and 174 MeV differential cross sections have been measured for the population of 12C*(0, 4.4, 7.7, 9.6, 14.1, 19.6). The population of 12C*4.4 + 12C*4.4 is also reported (1973AN22).
The relative population of elastic and inelastic channels is very energy dependent: see 24Mg in (1973ENVA) and (1968WI1C, 1973EM03, 1973GO01, 1973RE13, 1973RE12, 1973WI09, 1974RA1J, 1974RA1K, 1974SH16, 1974SP06, 1974VO09, 1975OB1B).
See also (1969BR1D, 1969BR1G, 1969HE06, 1970BR1G, 1973BR1C, 1973PE1D, 1973ST1A, 1974ST1L), (1968IM1A, 1969IM1A, 1969MI1B, 1969VO1E, 1970AN1D, 1970MI1D, 1970MO35, 1970PR12, 1971MC1J, 1971RI1F, 1971RI1G, 1972AR11, 1972FI11, 1972GO1G, 1972MA74, 1972MI1H, 1972RE1K, 1972RI19, 1973BO06, 1973CO1X, 1973FI07, 1973JA22, 1973MO1J, 1973SC1K, 1974FI1G, 1974GA1L, 1974KO1N, 1974PA08, 1974WA02; theor.) and (1968AR1C, 1970NA1F, 1971BA1A, 1972MI1H, 1973AR1E, 1973CL1E, 1973GR1G, 1974AR2B, 1974CO1L, 1975SW1A; astrophys. questions).
Elastic angular distributions in reaction (a) have been studied at E(12C) = 15 and 19 MeV (1971BO52, 1971BO1U, 1972BO68), at 20 to 36 MeV (1972CH1H, 1973CH1L; and also to 12C*(4.4) and various states in 13C) and at 87 MeV (1971LI11). See also (1970GO1B, 1971WI1J, 1973BR1C, 1973GO01, 1973SC1B) and 13C in (1976AJ04). Elastic angular distributions in reaction (b) are reported at E(12C) = 12 to 20 MeV (1972BO68).
Angular distributions have been measured at E(14N) = 21 MeV (1971BO1U, 1971VO01: to g.s.), 22.5 MeV (1969HE06: to g.s.), 65, 84 and 88 MeV (1971KO11: to g.s.), 78 MeV (1970VO02: to g.s., 4.4) and 155 MeV (1974BI1E: to g.s., 4.4, 7.7, 9.6, 10.8, 11.8, 12.7, 13.4, 14.1; see also reaction 54). See (1968AJ02) for earlier measurements. See also 14N in (1976AJ04), (1974AN36) and (1974NA1G). For yield measurements see 26Al in (1973ENVA) and (1974JO1J, 1974ST1N). See also (1969BR1D) and (1972MA74, 1974GA1L; theor.).
Elastic angular distributions have been measured at E(16O) = 20, 24, 35 and 42 MeV (1968VO1A, 1969VO10), 26, 30 and 32.5 MeV (1969KR03), 27 to 53 MeV (1972MA29, 1972MA1P), 36 MeV (1971OR02) and 65 and 80 MeV (1973GU12). At E(16O) = 65 and 80 MeV, angular distributions involving 12C*(0, 4.4) and various states of 16O have been studied by (1973GU12): see 16O in (1977AJ02).
A kinematically complete study of reaction (b) has been carried out at E(16O) = 58.3 MeV. The main process appears to involve (12C + α) corresponding to an excited state of 16O with Ex ≈ 10 MeV. Formation and decay of compound states in 24Mg are also involved (1974WI05). See also (1973ENVA).
See also (1970JA1B), (1969BR1D, 1969BR1G, 1969HE06, 1970BL1E, 1970BR1G, 1971GA1P, 1972GA1E, 1973PA1J, 1973PE1D, 1973ST1A), (1969KA1G, 1969RO1G, 1969VO1E, 1970AN1D, 1970CL1E, 1971DA30, 1972BA73, 1972CH1E, 1972GO1G, 1972MA1U, 1972RI03, 1973DE40, 1973FE1G, 1973LO02, 1973SA1K, 1974GA1L, 1974WA02, 1975KI01; theor.) and (1970NA1F, 1971WO1E, 1973AR1E, 1973CL1E, 1974CO1L, 1975SW1A; astrophys. questions).
The decay is mainly to the ground state via an allowed transition. Branching ratios to other states of 12C are displayed in Table 12.24 (in PDF or PS). The half-life is 10.97 ± 0.04 msec: see Table 12.28 (in PDF or PS) in (1968AJ02). Since transitions to 12C*(g.s., 4.4) are allowed Jπ(12N) = 1+.
Recent measurements of the ratios of the branching ratios, 12N/12B, for the decays to 12C*(4.4) is 1.52 ± 0.06 (1972AL31), 1.74 ± 0.08 (1974MC11). Using R = 1.63 ± 0.11, and other data, (1974MC11) find that the asymmetry in the decay to the excited state is δ4.44 = -0.013 ± 0.066 and that δg.s. = 0.1155 ± 0.0085. See also (1973KU1D; theor.).
12C*(12.7), populated in an allowed transition, decays primarily to 8Be*(2.9) [Jπ = 2+]; the absence of decay to 8Beg.s. is in agreement with the assignment Jπ = 1+ (1966SC23). The ft values for the β-transitions to 12C*(12.7, 15.1) agree well with shell-model calculations of (1965CO25). The agreement strongly suggests a close relation between 12C*(12.7) [Jπ = 1+; T = 0] and 12C*(15.1) [Jπ = 1+; T = 1]. See also (1971MI06, 1973CH16, 1973MIYZ).
See also (1968DA1J) and (1969BL1D, 1969CH1A, 1969CH1F, 1970JA1K, 1970ST04, 1971BL06, 1971KI04, 1971KI11, 1971LA21, 1971LI1F, 1971LI1H, 1971WI18, 1971WI1C, 1972EM02, 1972OC01, 1972WI28, 1972WI1C, 1973EM1B, 1973HA49, 1973TO14, 1973YO04, 1974HO1D, 1974WI1L, 1974WI1Q, 1975GR03; theor.).
At Ebs = 28 MeV, 4.4 and 15.1 MeV γ-rays have been observed corresponding to the population of 12C*(4.4, 15.1), while at Ebs = 21 MeV only 12C*(4.4) is excited (1971MU11). See also (1971WI1N), (1973KI1J; theor.) and 13C in (1976AJ04).
Angular distributions of the d0 and d1 groups to 12C*(0, 4.4) have been measured at Ep = 8 and 12 MeV (1966GL01), 17 MeV (1961BE12), 50 MeV (1970SC02) and 54.9 MeV (1968TA08). In addition angular distributions have also been measured for the groups to 12C*(12.7, 15.1, 16.1) at the two higher energies (1968TA08, 1970SC02). 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 the 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). At Ep = 17 MeV (1969CO06) give the ratio of σ(p, d)/σ(p, d-bar) to the ground state of 12C as 17. (1971OT02) suggest, however, that a part of the apparent (p, d-bar) cross section may be due to 12C + n final state interaction through 13C*(10.75). 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 (1967SP09, 1970VA1K) and 13C, 13N and 14N in (1976AJ04).
Angular distributions have been obtained at Ed = 0.41 to 0.81 MeV (1971PU01: t0), 1.0 to 2.7 MeV (1970LI1E, 1971LI1K: t0), 2.2 and 3.3 MeV (1954HO48: t0), 8 and 12 MeV (1966GL01: t0, t1), 12.1, 13.3 and 14.0 MeV (1968TE04: t0, t1), 13.6 MeV (1973ZA06: t0, t1), 14.8 MeV (1960MA10: t0, t1, t2), 15 MeV (1974LU06) and 28 MeV (1972BR27). In the latter experiment (1972BR27) have studied the triton groups to 12C*(12.7, 15.1, 16.1) [Jπ; T = (1+; 0), (1+; 1) and (2+; 1), respectively] and the 3He groups, in the analogue reaction, to 12B*(0, 0.95) [Jπ = 1+; T = 1 and Jπ = 2+; T = 1, respectively]. The relative yield to 12C*(15.1) is greater than that to its analogue, 12Bg.s., while the yields to the 2+ states are in good agreement. The value of β required to give the observed ratio of yields for the 1+ states is 0.13 [in good agreement with the (d, d') results: see reaction 49]: the charge-dependent matrix element is then 250 ± 50 keV (1972BR27). See also 15N in (1976AJ04), (1967SP09, 1969DE1H) and (1969LI1D; theor.).
Angular distributions have been measured at many energies up to E(3He) = 45 MeV: see (1968AJ02) for the earlier references and (1971BO26: 1.5 to 5.3 MeV; α0, α1, α2) and (1968AR12: 19.1, 27.3, 35.7, 36.8 MeV; α0, α1, α2, α3 and α to 12C*(12.7, 15.1, 16.1)). Angular correlations of α-particles and 4.4 MeV γ-rays have been studied at E(3He) = 4.5 MeV (1962HO13) and for αγ15.1 at 9.4 and 11.2 MeV (1969TA09). See also (1975MA2J).
Attempts have been made using this reaction (1970AR30, 1970RE09, 1974BA42) and reactions 49 and 66 to study the T mixing between the 1+ states 12C*(12.71, 15.11). Reported values for Γα/Γ for 12C*(15.11) are 1.2 ± 0.7% (1970RE09, 1970RE1F), 6.0 ± 2.5% (1970AR30), 4.1 ± 0.9% (1974BA42). The (1974BA42) value was obtained by observing the decay α-particles in reaction (b): adopting this value, and using the other parameters for the decay of 12C*(15.11) [see Table 12.9 (in PDF or PS)] leads to Γα = 1.8 ± 0.3 eV. If this isospin forbidden α-width is the result of mixing between the two 1+ states via a charge-dependent interaction, the matrix element is 340 ± 60 keV (1974BA42). (1970RE09) have measured branching ratios for the decays of 12C*(12.7, 15.1): see Table 12.9 (in PDF or PS). See also 16O in (1977AJ02).
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 have been obtained for reaction (a) at E(16O) = 14, 17 and 20 MeV (1968KN1A, 1971BA68: 12Cg.s + 17O*(g.s., 0.87)), 41.7 and 46.0 MeV (1973DE21). See also 28Si in (1973ENVA) and (1974BE1J; theor.).
Angular distributions have been measured at Ep = 14.5 MeV (1971CU01: t0), 18.5 MeV (1963LE03: t0) and 39.8 MeV (1970OL1B, 1973HO10: t0, t1). At Ep = 50.5 MeV the excitation of a T = 2 state with Ex = 27.595 ± 0.020 MeV is reported by (1970NE1A, 1971NE1B, 1971NE1E; unpublished results). This state has also been observed at Ep = 54 MeV as has another narrow state at Ex = 29.6 ± 0.1 MeV. The angular distribution of the tritons to the lower state is consistent with L = 0; that for the higher state is rather featureless (D. Ashery, private communication). [See also reaction 24 in 12B.] See also (1971KA04; theor.).
Angular distributions of the t0 group have been measured at En = 14 - 15 MeV: see (1968AJ02). The γ-ray from 12C*(4.4) has been seen: Eγ = 4436 ± 5 keV (1971NY03). See also 15N in (1976AJ04) and (1971MI1H).
Angular distributions have been studied at Ep = 7.53, 8.03, 9.54 and 10.54 MeV (1970ME30: g.s.), 20.5, 24.3, 29.4, 34.6, 40.1 and 44.6 MeV (1974PI05: g.s., 4.4), 39.8 MeV (1973HO10: g.s., 4.4) and 50 MeV (1970SC02: g.s., 4.4, 12.7, 14.1, 15.1, 16.1). The results of (1970SC02) strongly indicate Jπ = 4+ for 12C*(14.1). See also 15O in (1970AJ04, 1976AJ04), (1968SH11, 1968TO1E) and (1970CH1E; theor.).
Observed α-particle groups are shown in Table 12.23 (in PDF or PS) (1956DO41, 1965PE17, 1965SC12, 1972FA07). Angular distributions have been measured at many energies up to Ed = 28.5 MeV: see (1968AJ02) for the earlier work and (1969GO14: 1.0 - 3.1 MeV; α0 → α3), (1971AR41: 1.70, 2.30, 2.90 MeV; α0, α1, α2), (1967BO37: 2.29 - 5.76 MeV; α0, α1), (1969CU08: 10.5 MeV; α0 → α3), (1970SC02: 15 to 20 MeV; α0, α1 and α to 12C*(12.7, 14.1)), (1968SC1C: 17 MeV; α1 → α3 and α to 12C*(12.7, 14.1)), (1968MA1K: 20 MeV; α0 → α3 and α to 12C*(12.7, 14.1)) and (1967VI03: 28.5 MeV; α0, α1. At Ed = 40 MeV the upper limits for the ratio of the cross sections to 12C*(15.11) and 12C*(12.71) are ≈ 0.3% for θlab = 6° to 10° and 0.5% at 40° and 50°: these results by (1974VA15) imply a lower isospin mixing between these two 1+ states than suggested by the work of (1972BR27): see reactions 49, 66 and 67. For reaction (b) see (1972FA07). See also 16O in (1977AJ02), (1967SP09) and (1968DA1K, 1968ZE1B, 1969JO23, 1970JA1J; theor.).
At Eα = 42 MeV, angular distributions of 6Li ions corresponding to transitions to 12C*(0, 4.4) have been measured by (1964ZA1A). Reaction (b) at Eα = 22.9 MeV proceeds by sequential decay via states in 14N, 16O or 6Li to 12Cg.s. (1969BA17): see also 6Li in (1974AJ01), 14N in (1970AJ04) and 16O in (1971AJ02).
Angular distributions of α0 and α1 have been measured for Ep up to 18.6 MeV (see (1968AJ02)) 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, 7.66, 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 (1972CA1N, 1973CL1E; astrophys. questions) and (1967SP09).
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).
For reaction (a) see (1968AJ02). Reaction (b) appears to proceed primarily via excited states of 13N and 16O to 12C*(0, 4.4): see (1971EP03: Ep = 46.8 MeV) and (1972BO71: Ep = 50 MeV), 13N in (1976AJ04) and 16O in (1971AJ02, 1977AJ02). At Ep = 160 MeV, unpublished measurements by S.L. Kannenberg quoted by (1971EP03) show that reaction (b) proceeds in part by quasi-elastic scattering to 12Cg.s.. See also (1970GO12).
Angular distributions have been determined at Ed = 13.6 and 14.6 MeV (1974GA30: g.s.), 14.6 MeV (1964DA1B: g.s.), 19.5 MeV (1971GU07: g.s., 4.4), 28 MeV (1972BE29, 1972BE1T: g.s., 4.4), 35 MeV (1975BE01: g.s.) and 55 MeV (1971MC04: g.s., 4.4, 7.7, 9.6, 14.1). See also (1969KE1C, 1972CO23), (1967OG1A, 1972GA1E) and (1971DR02, 1972RO1L, 1974DO03, 1974KU05; theor.).
Angular distributions have been measured at E(3He) = 25.5 to 29 MeV (1972PI1A: 12C*(0, 4.4) + 7Be*(0, 0.4)) and 30 MeV (1970DE12: 12C*(0, 4.4, 9.6) + 7Be*(0, 0.4), 12C*(7.6) + 7Be(0)). See also (1971DE37, 1973PI1B, 1973ST1N) and (1972RO1L, 1973KL1B; theor.). (1975AU01) report the extraction of the α-particle pickup spectroscopic factor Sα using a finite range DWBA analysis (E(3He) = 26 MeV).
Reaction (a) at Eα = 25 MeV proceeds in part by sequential decay via states in 16O and 20Ne (1968PA12): see (1971AJ02, 1972AJ02). See also (1971BR1G, 1972SH1J). Angular distributions for the transitions to 12C*(0, 4.4) in reaction (b) have been studied at Eα = 35.5 to 41.9 MeV (1965BR13) and 65 MeV (1973WO06). The excitation of 12C*(9.6, 14.1) is also reported (1973WO06, 1974WO1D). See also (1972SH10; theor.) and (1973SC1B).
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). See also (1971SI1F, 1973PE1D, 1974ER1A), 20Ne in (1978AJ03) and 32S in (1973ENVA).
See (1963DE02; unpublished).