(See Energy Level Diagrams for 11B)
GENERAL: See also (1968AJ02) and Table 11.3 [Table of Energy Levels] (in PDF or PS).
Shell model: (1968GO01, 1970CO1H, 1971BA2Y, 1971NO02, 1972LE1L, 1973HA49, 1973KU03, 1973SA30, 1974ME19).
Cluster and collective models: (1969BA1J, 1970BA1Q, 1971NO02, 1972LE1L, 1973KU03).
Special levels: (1968GO01, 1969HA1G, 1969HA1F, 1970FR1C, 1971NO02, 1972MS01, 1973MA1K, 1973SA30, 1974IR04).
Electromagnetic transitions: (1967WA1C, 1969HA1G, 1969HA1F, 1969WA1C, 1970AL1E, 1972KE36, 1972MU1B, 1972TA21, 1972NA05, 1973HA49, 1973SA30, 1974ME19, 1974MU13).
Astrophysical questions: (1967MI1A, 1972CL1A, 1972KO1E, 1973AU1H, 1973CA1B, 1973CO1B, 1973LA19, 1973RE1G, 1973TI1A, 1973TR1B, 1973WE1D, 1974AU1A, 1974BO1K, 1974JA11, 1974MO1G, 1974RE1A, 1974WO1G).
Special reactions: (1968HA1C, 1968YI01, 1969DA1D, 1969GA18, 1969YI1A, 1971AR02, 1971BA16, 1973KO1D, 1973KU03, 1973LA19, 1973WI15, 1974BA70, 1974BE58, 1974FO22, 1974JA11, 1974LA18, 1975CR01, 1975KU01, 1975PO02).
Muon capture and muon reactions: (1968DE20, 1969BE41, 1969WU1A, 1970FA15, 1970VA24, 1971BE57, 1971BU11, 1971DE2D, 1972BE71, 1972MI15†).
†(1972MI15) have observed the γ-decay of 11B*(2.12).
Pion capture and pion reactions: (1968BO32, 1968GR1C, 1968LO1A, 1968NO1A, 1968NY1A, 1968RI1H, 1968TA1C, 1968WI1B, 1969AG1A, 1969BU1C, 1969MO1E, 1970BA1E, 1970LI1H, 1971BA16, 1971BE85, 1971FA09, 1971KA62, 1971NO08, 1972HU1A, 1973AL1D, 1973CH20, 1973JA1J, 1973NY04, 1974HU14, 1974KA07, 1974LE12, 1974TA18).
Kaon reactions: (1972BA09, 1973CH1M).
Other topics: (1968BU1B, 1968GO01, 1968ME13, 1970CO1H, 1971BA2Y, 1972AN05, 1972CA37, 1972LE1L, 1972MU1B, 1972PN1A, 1973CL09, 1973JU2A, 1973KU03, 1973MA48, 1973RO1R, 1974IR04, 1974MO1H, 1974MU13, 1975KU01).
Ground state properties: (1967CO1D, 1967SH14, 1968PE16, 1968RO1E, 1969LE1B, 1969WU1A, 1971TA1A, 1971ZO03, 1972GL06, 1972LE1L, 1972VA36, 1973CO1P, 1973KU1L, 1973MA1K, 1973SA30, 1973SU1B, 1973SU1C, 1974HA27, 1974ME19, 1974MU13).
Q = 0.0386 b (1968SC18);
[Q = 0.04065 ± 0.00026 b (1970NE05; theor.)].
Angular distributions of the protons have been reported at E(6Li) = 2.0 MeV (1971PO1D; unpublished: Ex ≤ 8.0 MeV) and 2.4 to 9.0 MeV (1966KI09: Ex < 9.3 MeV). For γ-spectra see (1962BE24, 1969TH01) and Table 11.4 (in PDF or PS). τm, measured in this reaction and in reactions 7, 8 and 29 are shown in Table 11.5 (in PDF or PS) (1969TH01).
Resonances for capture radiation are displayed in Table 11.6 (in PDF or PS) (1951BE13, 1954HE22, 1967PA19). Angular distributions, branching ratios and correlations have been studied by (1959JO25, 1962GR07): they determine Jπ = 5/2-, 7/2-, 5/2- or (3/2+), 7/2+ and 5/2+, respectively for 11B*(4.45, 6.74, 8.92, 9.19, 9.28): see (1968AJ02) for a more complete discussion and Tables 11.4 (in PDF or PS) and 11.6 (in PDF or PS). See also (1969OM1A).
Cross section measurements have recently been carried out by (1968MA07) for Eα = 4.43 to 5.12 MeV (n0) and by (1972VA02) for Eα = 4.5 to 8.0 MeV (n0) and 5.7 to 8.0 MeV (n1). Results from these and previous measurements are displayed in Table 11.7 (in PDF or PS) (1957BI84, 1959GI47, 1963ME08). See also (1968DA1H).
See 10Be in (1974AJ01).
Excitation functions have been measured for Eα = 14 to 25 MeV (t0) and 18 to 25 MeV (t1): they are essentially smooth (1972VA34). See also 8Be in (1974AJ01) and (1974KA32; theor.).
The elastic scattering has been studied for Eα = 1.6 to 12 MeV (1966CU02), 2.5 to 4.5 MeV (1972BO07), 8.6 to 12.5 MeV and 17.0 to 22.5 MeV (1973KE13) and 12.0 to 18.0 MeV (1970BI1B, 1971BI12). The inelastic scattering, leading to 7Li*(0.48), has been studied at Eα = 1.6 to 12 MeV (1966CU02), 1.6 to 3.2 MeV (1967PA19), 2.5 to 4.5 MeV (1972BO07), 5.8 to 6.7 MeV (1975BA06) and 17.0 to 22.5 MeV (1973KE13). See also (1968AJ02) for earlier references.
Observed resonances are displayed in Tables 11.8 (in PDF or PS) and 11.9 (in PDF or PS) (1966CU02, 1967PA19). A weak structure at Eα ≈ 12.7 MeV and broad structures at Eα ≈ 12 to 15 MeV are reported by (1970BI1B, 1971BI12): it is not clear whether these correspond to states in 11B. (1973KE13) suggest that the deviations from smooth behavior in the excitation functions are due to the exchange of a triton cluster between two α-particles. See also 7Li in (1974AJ01).
Angular distributions of deuterons have been measured at E(7Li) = 3.3 MeV (1967GA06: d0 → d3) and 3.78 to 5.95 MeV (1967KI03: d0 → d3, d4+5, d6). For γ-spectra see (1962BE24, 1969TH01) and Table 11.4 (in PDF or PS). For τm see Table 11.5 (in PDF or PS) (1969TH01). See also 13C in (1976AJ04).
Angular distributions have been measured at E(7Li) = 2.10 to 5.75 MeV (1969CA1A: t0 → t3). For τm see Table 11.5 (in PDF or PS) (1969TH01). At E(7Li) = 79.6 MeV transitions are observed to several 11B states. 11Bg.s. is particularly strongly populated: 23 μb/sr, at 7.4° (1974CE06). See also (1974CE1A).
Radiative transitions have been observed to 11B*(0, 2.12, 4.45 + 5.02) at Ed = 0.5 to 1.4 MeV (1966ZI01) and 0.56 to 3.56 MeV (1970BA1R, 1971BA72). The 90° γ0 differential cross section has been measured for Ed = 0.5 to 5.5 MeV (1963SU09, 1966SU05, 1966SU1C) and 2.9 to 11.9 MeV (1974DE01, 1974DE39). The behavior of the γ0, γ1 and γ2+3 total cross sections and of the angular distributions of these γ-rays indicate two resonances at Ed = 1.98 ± 0.05 and 3.12 ± 0.05 MeV with Γlab = 225 ± 50 and 320 ± 100 keV, corresponding to 11B*(17.43, 18.37). The higher resonance was not observable in the γ2 + γ3 cross section which was not measured beyond Ed = 2.5 MeV. The maximum γ0 cross section observed is 10.1 ± 3.5 μb at Ed ≈ 0.96 MeV (1971BA72). (1974DE39) observe resonant behavior in the 90° γ0 cross section at Ed ≈ 3.4 and 9.65 MeV (11B*(18.6, 23.7)) in addition to a wide structure at 4.7 MeV (11B*(19.7)). The angular distributions of γ0 from 11B*(18.6, 23.7) are typical of E1 transitions. The (d, γ0) reaction appears to proceed via excitation of the T = 1/2 component of the giant dipole resonance in 11B.
The cross section follows the Gamow function for Ed = 70 to 110 keV (1955RA14). The fast neutron and γ-yield rise smoothly to Ed = 1.8 MeV except for a possible "resonance" at Ed ≈ 0.94 MeV. The fast neutron yield then remains approximately constant to 3 MeV: see (1968AJ02) for references. The excitation functions for n0 → n4, and n to 10B*(5.1, 6.57) have been measured for Ed = 14 to 16 MeV: no strong fluctuations are observed (1973PA14). Polarization measurements have been reported at Ed = 0.9 to 2.5 MeV (1970MI04: n0 → n4), 3.0 to 5.5 MeV (1974TH02: n0 → n5 and n to 10B*(5.1, 6.6)) and 3.0 and 3.5 MeV (1970SP1A, 1971SP1C: n0 → n4). For papers dealing with applications see (1971DA21, 1971EL1B, 1972LU1B, 1973AU1G, 1973WE1T, 1973WE19). See also (1972DA34, 1973SZ07), (1970MI1G; theor.) and 10B in (1974AJ01).
Recently measurements of proton yields have been carried out by (1974AN01: 0.3 to 0.9 MeV; p0, p1), (1974FR02: 0.6 to 2.7 MeV (p0), 1.0 to 2.7 MeV (p1)), (1972AR31: 0.75 to 2.25 MeV; p0), (1974BO42: 0.9 to 2.5 MeV; p0, p1), (1973SA1Q: 0.9 to 3.1 MeV; p0, p1) and (1970PO03: 4.5 to 6.0 MeV; p0, p1). From these and previous measurements it appears that the p0 and p1 yields show a resonance at Ed = 750 ± 15 keV [11B*(16.43)], Γ ≈ 40 keV (1974AN01) and the p1 yield a resonance at 1.85 MeV [11B*(17.33)], Γc.m. ≈ 1.0 MeV (1973SA1Q). [The latter is also reported in the yield of 3.37 MeV γ-rays by (1957MC35).] Broad maxima have also been reported at Ed ≈ 0.9 MeV, (1.3) and 2.1 MeV by (1952CA19: p0) [see also (1972AR31)] and at 1.3 MeV by (1957MC35: 3.37 MeV γ-ray). (1974FR02) report a broad resonance at Ed = 1.8 MeV and a sharp resonance at 2.3 MeV, in the p1 yield. See also (1968BE1E). Polarization of the protons has been studied at many energies in the range Ed = 1 to 21 MeV: see (1968AJ02) for the earlier work and (1968YU01: 7.0 MeV; p0), (1969CU10: 10.0 MeV; p0), (1970FI07: 10 and 12 MeV; p0, p1), (1971GR20: 11.8 MeV; p0), (1971BR44: 12 MeV; p0), (1972BU26: 12.0 MeV; p0, p1), (1968BA19, 1973JO10: 12.3 MeV; p0, p1). See also (1967SA06, 1972FI1E, 1973FI1C). See also 10Be in (1974AJ01).
The yields of α-particles, both α0 and α1, (reaction (b)) have been measured at Ed = 0.3 to 0.9 MeV (1974AN01), 0.5 to 2.3 MeV (1962BI11), 0.6 to 2.0 MeV (1974FR02), 0.9 to 2.2 MeV (1971SA27) and 8 to 12.4 MeV (1966DO1A; also α2 for Ed = 9 to 12.4 MeV). (1974AN01) report a weak indication of the 0.75 MeV resonance, observed in the proton yield, in the α0 yield. (1962BI11) find no clear indication of resonance structure. See also (1968BE1E, 1973SZ07) and 7Li in (1974AJ01).
The cross section for reaction (c) has been measured for Ed = 0.15 to 19 MeV: see (1968AJ02) for the earlier references and (1974AN01: 0.3 to 0.9 MeV; t0), (1974FR02: 0.6 to 2.0 MeV; t0), (1974BO42: 0.9 to 2.5 MeV; t0) and (1973SA1Q: 0.9 to 3.1 MeV; t0). There is no clear evidence of resonance structure: see, however, (1955JU10, 1955JU1B, 1958JU38). See also 8Be in (1974AJ01).
See also (1973BI1G), (1971EL1B: applied) and (1971KO41; theor.).
Excitation functions for elastically scattered deuterons have been measured for Ed = 0.4 to 1.8 MeV (1963RE16), 1.0 to 2.2 MeV (1972LO05), 1.0 to 2.5 MeV (1968MA1H), 4.5 to 6.0 MeV (1970PO03) and 5.0 to 7.0 MeV (1971DJ02). Polarization measurements involving the d0 group have been reported at Ed = 6.3 MeV (1971DJ02), 11.8 MeV (1971GR20) and 12.6 MeV (1971ZA04). See also (1970VE06, 1971SP1C) and 9Be in (1974AJ01).
Angular distributions are reported at Et = 1.1 MeV (1970MAZE; unpublished).
Proton groups have been observed to a number of 11B states: see Table 11.10 (in PDF or PS) (1959HI69, 1966BR18). See also (1970CA28). Angular distributions of many of these proton groups have been studied at E(3He) = 1.0 to 10.2 MeV: see (1968AJ02) for references and (1973SU07: E(3He) = 0.82 and 1.10 MeV). L assignments derived from the higher energy work (1960HI08) are also shown in Table 11.10 (in PDF or PS). Gamma ray branching ratios and multipolarities for 11B levels up to Ex = 9.19 MeV have been extensively studied by (1958FE70, 1961DO03, 1964AL22, 1965OL03): see Table 11.4 (in PDF or PS) and the discussion in (1968AJ02). Lifetime measurements are shown in Table 11.5 (in PDF or PS) (1969BEYX; abstract). See also (1970OG1A) and (1970LK1A; theor.).
Angular distributions have been measured at Eα = 27.0 (1975PU01: d0 → d6) and 28.3 MeV (1965KA14: d0 → d3). The predominant L-transfer are L = 0, 2; 0 and 0, respectively for 11B*(0, 2.12, 5.02). The angular distribution for 11B*(4.45) is flat (1975PU01). See also (1970OG1A) and (1971BU1K; theor.).
Angular distributions have been determined for seven α-groups at E(6Li) = 3 to 4 MeV: see (1968AJ02). Angular distributions have also been obtained at E(6Li) = 24 MeV to 11B*(0, 2.12) and to a number of unresolved levels with Ex ≤ 13.2 MeV (1967CH34, 1968DA20). See also (1970OG1A).
The breakup reactions (reactions (b), (c) and (d)) have been studied at E(6Li) = 3.5 MeV by (1968JA08): reaction (b) goes mainly via a sequential process involving 11B*(10.3, 11.4, 12.6, 13.16, 13.5). The results for reaction (c) are not conclusive. 11B*(12.6, 13.16) may possibly contribute to reaction (d) (1968JA08).
For reaction (a) see (1964CA18). For reaction (b) see (1970LK1A; theor.).
The yield of ground state γ-rays has been measured at 90° for Ep = 0.6 to 6.3 MeV. Observed resonances are displayed in Table 11.11 (in PDF or PS). The anomaly observed at Ep = 1.05 MeV may not correspond to a state in 11B: it occurs at the threshold for 10B*(0.72) + n. The other four resonances correspond to states in 11B whose energies match well with those of the first four states in 11Be: T = 3/2. Several known T = 1/2 states in 11B are not observed in this reaction: see Table 11.3 (in PDF or PS) (1970GO04, 1973GO09).
The thermal capture cross section is 0.5 ± 0.2 b (1973MU14). For a listing of the observed capture γ-rays see Table 11.12 (in PDF or PS) (1967TH05). The τm for 11B*(6.74) is 10+12-8 fsec (1969WE07). See also (1973AR1M, 1974AR1K, 1974ST1C) and (1968FOZY; astrophys.).
The "free" neutron scattering cross section, (σ-bar)s = 2.23 ± 0.06 b. The coherent scattering amplitude (bound) is a = +1.4 ± 0.5 fm (1973MU14). See also (1969BA1P). The total scattering cross section is constant at 2.23 ± 0.06 b for En = 0.7 to 10 keV and then rises to 2.97 b at En = 127 keV (1970AS10).
Total cross section measurements in the range En = 10 to 500 keV confirm the broad maximum near En = 0.23 MeV, originally suggested by (1951BO45) and also observed in the (n, α) cross section (1966MO09). At higher energies the total cross section shows broad maxima at En = 1.9 and 2.8 MeV (1951BO45) and at 4.3 MeV (1961FO07): see Table 11.13 (in PDF or PS). In the range En = 5.5 to 16 MeV σtot is constant at 1.5 b (1961FO07).
Polarization measurements (0.075 to 2.2 MeV and 2.63 MeV) and measurements of differential cross sections (0.075 to 4.4 MeV) by (1971LA10, 1973CO05, 1973HA2G, 1973HA64) have been analyzed using R-matrix calculations: the results are shown in Table 11.14 (in PDF or PS). They are consistent with results from 10B(n, n'γ) and 7Li(α, n).
Elastic scattering differential cross sections are also reported at En = 7.02 and 7.55 MeV (1969HO1G) and at 9.72 MeV (1970CO12). See also (1969MA39, 1970PO1E), (1967IR1A, 1972LA1F) and (1966AG1A, 1967BE1F; theor.).
The yield of 0.7 MeV γ-rays has been studied from threshold to En = 5.2 MeV: observed resonances are displayed in Table 11.13 (in PDF or PS) (1960DA08). See also (1970NE03). Inelastic scattering cross sections for formation of various 10B states have been measured by (1970NE03: En = 1.45 to 4.90 MeV, and 14.8 MeV), (1969HO1G: En = 7.02 and 7.55 MeV) and (1970CO12: En = 9.72 MeV). See also 10B in (1974AJ01) and (1969RO1F).
The thermal cross section is < 0.2 b (1973MU14). See also 9Be in (1974AJ01) and (1970NE03).
See 9Be in (1974AJ01).
The cross section for reaction (b) has been measured for En = 1.4 to 8.2 MeV by (1961DA16). Fluctuations are observed at some of the resonant energies in the 10B(n, α) reaction: see Table 11.13 (in PDF or PS). See also (1968ST1D) and (1969AN25, 1971AN1M).
The "recommended" value of the thermal isotropic absorption cross section is 3837 ± 9 b (1973MU14). See also (1970ME1F). The ground state branching for thermal neutrons is 6.308 ± 0.006% (1967DE15). See also (1968MA07), and (1968AJ02) for earlier references. The cross section for En = 10 eV to 200 keV is given by the expression
The cross section for the (n, α0) reaction has been calculated by (1968MA07) from that for the 7Li(α, n) reaction: En = 30 to 516 keV.
The α1 cross section has been measured for En = 47 keV to 4.9 MeV and at 14.8 MeV (1970NE03): the cross section is substantially higher than that reported by (1961DA16). Observed resonances are displayed in Tables 11.13 (in PDF or PS) and 11.14 (in PDF or PS) (1961DA16).
Other recent measurements include those by (1969BO03) at En = 30 to 800 keV (relative cross sections for α0 and α1) and by (1969AN25) at 14.4 MeV (cross section for formation of α0 + α1, α2). (1972HA04) have calculated differential cross sections for α0 and α1 based on R-matrix parameters derived from neutron elastic scattering, polarization measurements and (n, α) data. See also (1974HA1W, 1975HA1G; theor.). See also 7Li in (1974AJ01), (1968GI1D, 1968GU1B, 1968ST1D, 1970DE1H, 1972LA1F, 1975FR1B), (1964FO1A; astrophys.) and (1968MO1D, 1968PA1E, 1973FA1M, 1973LI1E; applied).
Angular distributions for proton capture to 11B*(0, 2.15 ± 0.10) have been measured at Ep = 185 MeV. The population of 11B*(4.45 + 5.02) and of unresolved higher states is also observed but an attempt to observe T = 3/2 analogue states in 11B and 11N (the latter populated via (p, π-)) was unsuccessful (1974DA27).
Proton groups reported by (1951VA1A, 1963EL12, 1961JA23, 1966BR18) are listed in Table 11.15 (in PDF or PS). Angular distributions have been studied at many energies in the range Ed = 0.17 to 28 MeV [see (1968AJ02) for a listing of the earlier references] and (1970HU1B: 0.35 MeV; p0 → p3, p4+5, p6, p7), (1973CO18: 0.67 to 2.32 MeV; p4+5), (1970PO03: 4.5 to 5.5 MeV; p0 → p3) and (1967GO27: 13.6 MeV; p0). The lowest five levels are formed by ln = 1 except for 11B*(2.12) which appears to involve a spin-flip process. They are presumed to comprise the set 3/2-, 1/2-, 5/2-, 3/2-, 7/2- expected as the lowest p7 levels (a/K ≈ 4.0). 11B*(9.19, 9.28) [Jπ = 7/2+ and 5/2+, respectively] show strong l = 0 stripping and are ascribed to capture of a 2s neutron by 10B: see (1968AJ02) for a listing of all the relevant references. The probability p3/2 for transfer of a neutron with angular momentum 3/2 has been determined for the p0 group using vector polarized deuterons with Ed = 10 and 12 MeV, and compared with shell model calculations of (1965CO25, 1967CO32), (1970FI07; and see also (1967SC29)).
Studies of pγ correlations are discussed in reaction 14 of (1968AJ02) and displayed in Table 11.4 (in PDF or PS) of this paper.
See also 12C, (1967CO30, 1967SP09, 1973BR24), (1973FO02) and (1969BO1F, 1969DO08, 1970DE35, 1970DO07, 1970DO13; theor.).
At Ed = 5.5 MeV, deuteron groups are observed to the ground state of 11B and to states at Ex = 2.126, 4.449, 5.027, 6.769, 6.806 and 7.301 MeV (± 10 keV). All the angular distributions appear to be characteristic of ln = 1 (1961BA10). See also 13C in (1976AJ04).
Angular distributions have been measured at Eα = 56 MeV for the ground state transitions in this, and in the analog (α, t) reactions: the average ratio of the (α, 3He) to the (α, t) differential cross sections is 1.2 ± 0.1 (1968GA1C, 1969GA11).
See (1969TH01) for reaction (a) and (1974KO1G) for reaction (b).
See (1968GA03) and (1968GO1K, 1970GO1B, 1970SC1G, 1973MC17, 1973OS03; theor.) and (1968AJ02).
The angular distribution has been measured at E(18O) = 20 and 24 MeV (1971KN05). See also (1974SW04).
The angular distribution has been measured at E(19F) = 20 and 24 MeV (1971KN05). See also (1968GA03) and (1970GO1B; theor.).
11Be decays to 11B*(0, 2.12, 5.02, 6.79, 7.98, 9.87): see Table 11.16 (in PDF or PS) for the parameters of the observed β and γ transitions (1971AL07). Delayed α-particles are also observed with a total Iα of 3.0%/decay. These α-particles are not observed to be in coincidence with 478 keV γ-rays [upper limit = 5% for Eα > 0.3 MeV], suggesting that they result from the decay of 11B*(9.87) to 7Lig.s. (1971AL07). The half-life of 11Be is 13.81 ± 0.08 sec (1970AL21). See also (1968AJ02) and (1974AL11).
Mean gamma widths of low-lying states obtained by resonance scattering and transmission studies are listed in Table 11.17 (in PDF or PS) (1958ME79, 1958RA14, 1959CO95, 1964BO22, 1965KE05, 1968CR07, 1973SA21, 1974LE1K). See also (1974WE1R) and (1968AJ02).
The giant dipole resonance is shown to consist mainly of T = 1/2 states in the lower energy region and of T = 3/2 states in the higher energy region by observing the decay to states in 10B and 10Be (reactions (a) and (b)) (1971PA10). Absolute measurements of the 11B(γ, all n) cross section from threshold to 28 MeV have been carried out by (1973HU09, 1973HU1D): the cross section exhibits a maximum at Eγ = 25.2 ± 0.1 MeV (σ ≈ 8 mb) in addition to some weaker structure. The integrated cross section from threshold to 27.6 MeV is 0.37 ± 0.04 in units of 60 NZ/A. The results are consistent with the photoabsorption cross section proceeding via T = 1/2 at lower energies (1973HU09). This is also the picture derived from the (γ, d0) cross section (reaction (c)): it peaks at ≈ 19 MeV, lower than it would if T = 3/2 states were involved (1974DE01). See also (1968KA38, 1969MU10, 1971KA70, 1972SL1B) and (1970HA28).
The cross section for (γ, n) shows many peaks in the range E γ = 12 to 28 MeV (1965HA19). (1969SO06, 1970SO03) report resonances at E γ = 12.4, 13.1, 13.65, 14.75, 15.1, 15.5, 15.85, 16.2, 16.5, 16.9, 17.5, (20.2), 21.6, 23.2, (24.5), 25.5, 27.7 and 29.2 MeV in the (γ, p) cross section. [See (1970SO03) also for Γγ and Jπ for the states below 18 MeV (mainly 5/2+), and for an evaluation of the structure reported by (1965HA19).] See also (1972BU1J, 1973SP02) and (1971DU11; theor.). For reactions (d) and (e) see (1959AJ76).
The charge-scattering radius is 1.55 fm (1959ME24). Magnetic elastic scattering at θ = 180° shows strong M3 effects: the derived ratio of static M3/M1, 2.9 ± 0.2 fm2, suggesting a j - j coupling scheme for 11Bg.s. (1966RA29). The quadrupole contribution to the elastic form factor is best accounted for by the undeformed shell model, Q = 3.72 ( ± 20%) fm2, r(r.m.s.) = 2.42 fm (1966IS1A, 1966ST12). The excitation of 11B*(2.1, 4.4, 5.0, 8.6, 8.9) has been studied by (1975KA02: Ee = 52 to 90 MeV). (1973FL1A) report the excitation of 11B*(7.30, 9.27) at the same Ee. The giant resonance region, centered at ≈ 18 MeV, is characterized by a lack of prominent features except for a pronounced peak at Ex = 13.0 ± 0.1 MeV (mixed M1 - E2) and a broad transverse group at Ex = 15.5 MeV (1975KA02).
Ground state transition widths for various excited states are listed in Table 11.17 (in PDF or PS) (1962ED02, 1966KO08, 1966SP02, 1967SP02, 1975KA02). For reaction (b) see (1971VL01, 1972VL1A) and 10Be in (1974AJ01). See also (1968AJ02), (1971RI1E), (1968GO1J, 1972THZF), (1968JA1D, 1969VI02, 1973DO01, 1973GA19, 1973RO11, 1973SP02; theor.).
Angular distributions of neutrons have been measured at En = 7.55 MeV (1969HO1G: n0 → n2), 9.72 MeV (1970CO12: n0 → n3, n4+5) and 14.1 MeV (1970AL08: n0 → n3, n4+5, n6). For branching ratios see Table 11.4 (in PDF or PS) (1972NI05). See also 12B, (1968AL1E, 1970PO1E) and (1968CA1A, 1969WA11, 1971MI12, 1971OT03, 1974BI07; theor.).
Observed proton groups are displayed in Table 11.18 (in PDF or PS) (1969SU03, 1971BR41, 1974KA15). Angular distributions have been measured at Ep = 12 to 21.5 MeV (1972TH1C), 30.3 MeV (1969KA15: p0 → p2), 100 MeV (1970HO07: p0 → p3), 155 MeV (1968GE04: p0 → p3, p4+5) and 185 MeV (1969SU03: p0 → p2 and p to 11B*(8.56, 8.92)). For an angular correlation experiment see (1970HU01). See also (1968AJ02), (1970TH1F, 1973CA1H), (1969WA11, 1971LO05, 1973KA04; theor.) and 12C. For reaction (b) see 10Be in (1974AJ01). The spectroscopic factors for the (t + 8Be) and (α + 7Li) cluster structures in 11B [as determined from a study of the 11B(p, α)8Be reaction] are ≈ 0.77 and ≈ 0.02, respectively (1972DE01, 1972DE02).
The elastic scattering has been studied at Ed = 5.5 MeV (1971HIZF) and 11.8 MeV (1967FI07). See also (1968VE11, 1968VE1C, 1970VE06, 1971TAZN) and (1969VE09, 1970EL16; theor.).
The elastic scattering has been studied at Et = 1.8 and 2.1 MeV (1969HE08, 1969SI12).
The elastic scattering has been studied at E(3He) = 8, 10, 12, 15 and 18 MeV (1969MI15, 1969PA11), 14 MeV (1970NU02) and 18.3, 20.6 and 27.2 MeV (1972BU30), and 74 MeV (1974AS06: also 11B*(4.45)). A coupled channel analysis of the 74 MeV results suggests a quadrupole deformation β2 = +0.43 or -0.50 for 11B (1974AS06). At E(3He) = 29.8 MeV a number of 11B states are populated, including suggested T = 3/2 states [see Table 11.19 (in PDF or PS)] with Ex = 12.51 ± 0.05, 12.98 ± 0.09 and 14.40 ± 0.05 MeV, with Γc.m. = 260 ± 50, 390 ± 120 and 220 ± 50 keV, respectively. There is a weak indication also of a state at Ex = 14.51 MeV (1971WA21). See also (1969AD1C, 1970BA1P, 1970DU07). For reaction (b) see (1972YO02).
Angular distributions have been reported at Eα = 28.3 MeV (1965KO1A: α0 → α3, α4+5, α6), 28.4 and 29.0 MeV (1968KA24: α0) and 28.5 MeV (1967NA06: α0 → α3, α4+5, α6, α8). For reaction (b) see (1969FU09).
The elastic scattering has been measured at E(6Li) = 28 MeV (1972BA52) and analyzed by the optical model.
See (1970LK1A; theor.).
See (1975HI1D), and (1967GU1A) for reaction (b).
The elastic scattering has been studied at E(11B) = 28 MeV (1969VO07, 1969VO10), at E(12C) = 15, 17, 20 and 24 MeV (1974BO15), and at E(12C) = 87 MeV (1971LI11). The population of 11B*(2.12, 4.45, 6.79) and of 12C*(0, 4.43) has also been reported: see (1969VO07). See also (1974DA1P) and (DE63Y, 1970AN1D; theor.).
The elastic scattering has been investigated at E(14N) = 41, 77 and 113 MeV (1971LI11).
The elastic scattering has been studied at E(16O) = 14.5 to 27.5 MeV (1968OK1B) and 27, 30, 32.5, 35 and 60 MeV (1969VO10, 1972SC03, 1974KO1P). See also (1969BR1D, 1971BO1V) and (1970SC1G, 1974DE17; theor.).
The fraction of transitions to the ground and to excited states of 11B [and to 11C states reached in the (γ, n) reaction] has been measured at Ebs = 24.5, 27, 33 and 42 MeV: the ground state is predominantly populated. The population of analog states in the (γ, n) and (γ, p) reactions are similar: see 11C (1970ME17). See also the discussions in (1973DI1C, 1973SP03, 1974DI17) and in 12C. Angular distributions of the p0+1 and the p2+3+4+5 groups have been measured by (1974FI17: Eγ = 60, 80, 100 MeV). See also (1968FR12) and (1970MU1D, 1971BI01, 1973MS01, 1973MS02; theor.).
At Ee = 497 MeV the excitation of 11B*(0, 2.1, 5.) has been observed by Auriol et al. (see (1972RA1E)). See also (1967AM1A), 12C and (1968BO1D, 1968CI1B, 1968WA1D, 1969BA1F, 1972BE59, 1974HA14; theor.).
Angular distributions have been measured at En = 56 MeV for the deuterons to 11B*(0, 2.12, 4.45 + 5.02) (1974KI1A).
Gross structure is seen in the summed proton spectrum with Q = -15.6 ± 0.6 and -34.3 ± 0.8 MeV (1965RI1A, 1966TY01), -15.0 ± 0.5 and -35.5 ± 1.0 MeV (1971LA16), corresponding to 11Bg.s. and an excited state with Jπ = 1/2+ at Ex ≈ 19.5 MeV (ejection of p- and s-protons, respectively). High resolution experiments show groups corresponding to 11B*(0, 2.12, 4.45, 5.02, 6.79) (1965PU02, 1967PU01, 1974ST1R). See also (1969EP01, 1971HA61, 1971HO03, 1972PU1A), (1968AJ02, 1969RU1A, 1973JA01), (1967KO1B, 1969MC13, 1970KA01, 1971YO1E, 1972KO13, 1972LI1J, 1972ST33, 1973GU18, 1973GU1D; theor.) and 12C.
Angular distributions of 3He ions have been measured at Ed = 20, 24, 28 MeV (1971IN1C; unpublished: to 11B*(0, 2.12, 4.45, 5.02, 6.74 + 6.79, 7.29, 7.98)), 28 MeV (1968GA13: to g.s.), 28 and 50 MeV (1968DU01: 11B*(0, 6.74)), 28.5 MeV (1966DE1C: to g.s.), 52 MeV (1968HI01: to 11B*(0, 2.12, 4.45, 5.02, 6.74 + 6.79, 7.29)) and 80 MeV (1974AS04: to 11B*(0, 4.45)). A coupled channels Born approximation analysis gives good agreement with the angular distributions: a positive β2 is suggested by the results (1974AS04): see, however, (1974KU17). See also (1969KA1A, 1973WA1E, 1974DI1A) and (1969TA1D, 1973ST16, 1974ST18; theor.).
Angular distributions of the α-particles to 11B*(0, 2.12) have been measured at Et = 1 to 2 MeV (1962GU01), 1.11 to 3.40 MeV (1969ET01 and private communication), 10.1 MeV (1962PU01) and 13 MeV (1965AJ01; also α2, α3). Electromagnetic transitions have been studied by (1968BE30): see Table 11.4 (in PDF or PS) (1968BE30) confirm J = 3/2 for 11B*(5.02). See also (1969AR1B) and (1969NA1C; theor.).
This reaction has been studied at E(10B) = 100 MeV: 11Bg.s. is much more strongly excited than 11B*(2.12) (1973YO1C, 1973YO1D). The ratios of the yields 11Bg.s./11Cg.s. and 11B*(2.12)/11C*(2.00) have been studied at 100 MeV. They differ from 1 by a few percent at certain angles: the deviations are more pronounced for the first excited states (1974HA1V).
The angular distribution involving the ground state transitions has been measured at E(12C) = 114 MeV (1974AN36). See also (1967WI04, 1969BR1G).
See (1966PO1B, 1967BI06, 1967VO1A, 1974AN36). See also (1969BR1D, 1973SC1J) and 15O in (1976AJ04).
At E(19F) = 40, 60 and 68.8 MeV angular distributions involving 20Ne g.s. + 11Bg.s., 20Ne*1.63 + 11Bg.s. and 20Neg.s. + 11B*2.12 (E = 68.8 MeV only) have been measured by (1972SC03). See also (1969VO1D, 1970VO1F) and (1972BO21; theor.).
At Ep = 50.5 MeV, in addition to 11B*(0, 2.12, 4.45, 5.02, 6.74, 8.92), a state is observed at Ex = 12.94 ± 0.05 MeV, Γ = 350 ± 50 keV. Comparison of the angular distributions of the 3He and of the tritons [in the analog reaction] at Ep = 43.7 and 50.5 MeV lead to the assignments Jπ = 1/2-; T = 3/2 for this state and for 11C*(12.50): the strong proton and the weak α-decay are consistent with this assignment (1968CO26). The T = 3/2 state is also observed at Ep = 40 MeV by (1974BE20): Ex = 12.91 ± 0.03 MeV, Γ = 260 ± 50 keV. 11B*(12.55, 14.33) reported by (1970GO04) in the 10Be(p, γ)11B reaction are not observed by (1974BE20): see Table 11.19 (in PDF or PS). Angular distributions have been measured to 11B*(0, 2.12, 4.45, 5.02) at Ep = 26.9 to 43.1 MeV (1975MI01) and at 43.7 and 49.6 MeV (1968FL02). See also (1969SC1F).
Observed proton groups are displayed in Table 11.18 (in PDF or PS) (1970BR23). Angular distributions are reported at Ed = 0.41 to 0.81 MeV (1971PU01: α0, α1), 1.0 to 2.7 MeV (1970LI1E: α0, α1), 1.4 MeV (1966KL1A: α0), 3.3 to 4.2 MeV (1963MA24: α0), 6.8 MeV (1968DE26: α0 → α3), 11.7 MeV (1969CU08: α0 → α3) and 12.1, 13.3 and 14.1 MeV (1970KL04: α0 → α3). See also (1968AJ02), (1967SP09, 1968CO04, 1971LI1K) and 15N.
Angular distributions of the α0 → α3 groups have been measured at Ep = 18 MeV (1962BR34).
Angular distributions for the α0 and α1 groups have been measured at En = 4.9 MeV (1972KI12), 14.1 MeV (1968BA30 [also α2+3], 1968HS03 [also α2, α3, α4+5], 1968MA11, 1973BO26), 14.8 to 18.8 MeV (1971SA31) and 14.9 MeV (1968LE11). See also (1969DI1B, 1970DI1A, 1974TU1A). The angular distribution of the 2.12 MeV γ-ray (Eγ = 2118 ± 5 keV) is isotropic; that for the 4.4 MeV γ-ray shows a weak anisotropy. Both γ-rays are Doppler broadened: τm < 100 fsec [see Table 11.5 (in PDF or PS)] (1972NY02). See also (1971NY03) and 15N in (1976AJ04).
At En = 14.1 and 15.7 MeV various states of 11B with 8.9 < Ex < 14.5 MeV appear to be involved in the sequential decay to 7Li. Angular correlation results are consistent with Jπ = 7/2 and 5/2 for 11B*(9.19, 9.28), respectively (1971SC16).
At Eα = 72.5 MeV, the excitation of 11B*(0, 2.12, 4.45, 5.02, 6.74) is reported (1974WO1D).