
^{11}B (1975AJ02)(See Energy Level Diagrams for ^{11}B) 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 γdecay of ^{11}B*(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Angular distributions of the protons have been reported at E(^{6}Li) = 2.0 MeV (1971PO1D; unpublished: E_{x} ≤ 8.0 MeV) and 2.4 to 9.0 MeV (1966KI09: E_{x} < 9.3 MeV). For γspectra see (1962BE24, 1969TH01) and Table 11.4 (in PDF or PS). τ_{m}, 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 J^{π} = 5/2^{}, 7/2^{}, 5/2^{} or (3/2^{+}), 7/2^{+} and 5/2^{+}, respectively for ^{11}B*(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 E_{α} = 4.43 to 5.12 MeV (n_{0}) and by (1972VA02) for E_{α} = 4.5 to 8.0 MeV (n_{0}) and 5.7 to 8.0 MeV (n_{1}). Results from these and previous measurements are displayed in Table 11.7 (in PDF or PS) (1957BI84, 1959GI47, 1963ME08). See also (1968DA1H).
Excitation functions have been measured for E_{α} = 14 to 25 MeV (t_{0}) and 18 to 25 MeV (t_{1}): they are essentially smooth (1972VA34). See also ^{8}Be in (1974AJ01) and (1974KA32; theor.).
The elastic scattering has been studied for E_{α} = 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 ^{7}Li*(0.48), has been studied at E_{α} = 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 E_{α} ≈ 12.7 MeV and broad structures at E_{α} ≈ 12 to 15 MeV are reported by (1970BI1B, 1971BI12): it is not clear whether these correspond to states in ^{11}B. (1973KE13) suggest that the deviations from smooth behavior in the excitation functions are due to the exchange of a triton cluster between two αparticles. See also ^{7}Li in (1974AJ01).
Angular distributions of deuterons have been measured at E(^{7}Li) = 3.3 MeV (1967GA06: d_{0} → d_{3}) and 3.78 to 5.95 MeV (1967KI03: d_{0} → d_{3}, d_{4+5}, d_{6}). For γspectra see (1962BE24, 1969TH01) and Table 11.4 (in PDF or PS). For τ_{m} see Table 11.5 (in PDF or PS) (1969TH01). See also ^{13}C in (1976AJ04).
Angular distributions have been measured at E(^{7}Li) = 2.10 to 5.75 MeV (1969CA1A: t_{0} → t_{3}). For τ_{m} see Table 11.5 (in PDF or PS) (1969TH01). At E(^{7}Li) = 79.6 MeV transitions are observed to several ^{11}B states. ^{11}B_{g.s.} is particularly strongly populated: 23 μb/sr, at 7.4° (1974CE06). See also (1974CE1A).
Radiative transitions have been observed to ^{11}B*(0, 2.12, 4.45 + 5.02) at E_{d} = 0.5 to 1.4 MeV (1966ZI01) and 0.56 to 3.56 MeV (1970BA1R, 1971BA72). The 90° γ_{0} differential cross section has been measured for E_{d} = 0.5 to 5.5 MeV (1963SU09, 1966SU05, 1966SU1C) and 2.9 to 11.9 MeV (1974DE01, 1974DE39). The behavior of the γ_{0}, γ_{1} and γ_{2+3} total cross sections and of the angular distributions of these γrays indicate two resonances at E_{d} = 1.98 ± 0.05 and 3.12 ± 0.05 MeV with Γ_{lab} = 225 ± 50 and 320 ± 100 keV, corresponding to ^{11}B*(17.43, 18.37). The higher resonance was not observable in the γ_{2} + γ_{3} cross section which was not measured beyond E_{d} = 2.5 MeV. The maximum γ_{0} cross section observed is 10.1 ± 3.5 μb at E_{d} ≈ 0.96 MeV (1971BA72). (1974DE39) observe resonant behavior in the 90° γ_{0} cross section at E_{d} ≈ 3.4 and 9.65 MeV (^{11}B*(18.6, 23.7)) in addition to a wide structure at 4.7 MeV (^{11}B*(19.7)). The angular distributions of γ_{0} from ^{11}B*(18.6, 23.7) are typical of E1 transitions. The (d, γ_{0}) reaction appears to proceed via excitation of the T = 1/2 component of the giant dipole resonance in ^{11}B.
The cross section follows the Gamow function for E_{d} = 70 to 110 keV (1955RA14). The fast neutron and γyield rise smoothly to E_{d} = 1.8 MeV except for a possible "resonance" at E_{d} ≈ 0.94 MeV. The fast neutron yield then remains approximately constant to 3 MeV: see (1968AJ02) for references. The excitation functions for n_{0} → n_{4}, and n to ^{10}B*(5.1, 6.57) have been measured for E_{d} = 14 to 16 MeV: no strong fluctuations are observed (1973PA14). Polarization measurements have been reported at E_{d} = 0.9 to 2.5 MeV (1970MI04: n_{0} → n_{4}), 3.0 to 5.5 MeV (1974TH02: n_{0} → n_{5} and n to ^{10}B*(5.1, 6.6)) and 3.0 and 3.5 MeV (1970SP1A, 1971SP1C: n_{0} → n_{4}). For papers dealing with applications see (1971DA21, 1971EL1B, 1972LU1B, 1973AU1G, 1973WE1T, 1973WE19). See also (1972DA34, 1973SZ07), (1970MI1G; theor.) and ^{10}B in (1974AJ01).
Recently measurements of proton yields have been carried out by (1974AN01: 0.3 to 0.9 MeV; p_{0}, p_{1}), (1974FR02: 0.6 to 2.7 MeV (p_{0}), 1.0 to 2.7 MeV (p_{1})), (1972AR31: 0.75 to 2.25 MeV; p_{0}), (1974BO42: 0.9 to 2.5 MeV; p_{0}, p_{1}), (1973SA1Q: 0.9 to 3.1 MeV; p_{0}, p_{1}) and (1970PO03: 4.5 to 6.0 MeV; p_{0}, p_{1}). From these and previous measurements it appears that the p_{0} and p_{1} yields show a resonance at E_{d} = 750 ± 15 keV [^{11}B*(16.43)], Γ ≈ 40 keV (1974AN01) and the p_{1} yield a resonance at 1.85 MeV [^{11}B*(17.33)], Γ_{c.m.} ≈ 1.0 MeV (1973SA1Q). [The latter is also reported in the yield of 3.37 MeV γrays by (1957MC35).] Broad maxima have also been reported at E_{d} ≈ 0.9 MeV, (1.3) and 2.1 MeV by (1952CA19: p_{0}) [see also (1972AR31)] and at 1.3 MeV by (1957MC35: 3.37 MeV γray). (1974FR02) report a broad resonance at E_{d} = 1.8 MeV and a sharp resonance at 2.3 MeV, in the p_{1} yield. See also (1968BE1E). Polarization of the protons has been studied at many energies in the range E_{d} = 1 to 21 MeV: see (1968AJ02) for the earlier work and (1968YU01: 7.0 MeV; p_{0}), (1969CU10: 10.0 MeV; p_{0}), (1970FI07: 10 and 12 MeV; p_{0}, p_{1}), (1971GR20: 11.8 MeV; p_{0}), (1971BR44: 12 MeV; p_{0}), (1972BU26: 12.0 MeV; p_{0}, p_{1}), (1968BA19, 1973JO10: 12.3 MeV; p_{0}, p_{1}). See also (1967SA06, 1972FI1E, 1973FI1C). See also ^{10}Be in (1974AJ01). The yields of αparticles, both α_{0} and α_{1}, (reaction (b)) have been measured at E_{d} = 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 α_{2} for E_{d} = 9 to 12.4 MeV). (1974AN01) report a weak indication of the 0.75 MeV resonance, observed in the proton yield, in the α_{0} yield. (1962BI11) find no clear indication of resonance structure. See also (1968BE1E, 1973SZ07) and ^{7}Li in (1974AJ01). The cross section for reaction (c) has been measured for E_{d} = 0.15 to 19 MeV: see (1968AJ02) for the earlier references and (1974AN01: 0.3 to 0.9 MeV; t_{0}), (1974FR02: 0.6 to 2.0 MeV; t_{0}), (1974BO42: 0.9 to 2.5 MeV; t_{0}) and (1973SA1Q: 0.9 to 3.1 MeV; t_{0}). There is no clear evidence of resonance structure: see, however, (1955JU10, 1955JU1B, 1958JU38). See also ^{8}Be in (1974AJ01). See also (1973BI1G), (1971EL1B: applied) and (1971KO41; theor.).
Excitation functions for elastically scattered deuterons have been measured for E_{d} = 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 d_{0} group have been reported at E_{d} = 6.3 MeV (1971DJ02), 11.8 MeV (1971GR20) and 12.6 MeV (1971ZA04). See also (1970VE06, 1971SP1C) and ^{9}Be in (1974AJ01).
Angular distributions are reported at E_{t} = 1.1 MeV (1970MAZE; unpublished).
Proton groups have been observed to a number of ^{11}B 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(^{3}He) = 1.0 to 10.2 MeV: see (1968AJ02) for references and (1973SU07: E(^{3}He) = 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 ^{11}B levels up to E_{x} = 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 E_{α} = 27.0 (1975PU01: d_{0} → d_{6}) and 28.3 MeV (1965KA14: d_{0} → d_{3}). The predominant Ltransfer are L = 0, 2; 0 and 0, respectively for ^{11}B*(0, 2.12, 5.02). The angular distribution for ^{11}B*(4.45) is flat (1975PU01). See also (1970OG1A) and (1971BU1K; theor.).
Angular distributions have been determined for seven αgroups at E(^{6}Li) = 3 to 4 MeV: see (1968AJ02). Angular distributions have also been obtained at E(^{6}Li) = 24 MeV to ^{11}B*(0, 2.12) and to a number of unresolved levels with E_{x} ≤ 13.2 MeV (1967CH34, 1968DA20). See also (1970OG1A). The breakup reactions (reactions (b), (c) and (d)) have been studied at E(^{6}Li) = 3.5 MeV by (1968JA08): reaction (b) goes mainly via a sequential process involving ^{11}B*(10.3, 11.4, 12.6, 13.16, 13.5). The results for reaction (c) are not conclusive. ^{11}B*(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 γrays has been measured at 90° for E_{p} = 0.6 to 6.3 MeV. Observed resonances are displayed in Table 11.11 (in PDF or PS). The anomaly observed at E_{p} = 1.05 MeV may not correspond to a state in ^{11}B: it occurs at the threshold for ^{10}B*(0.72) + n. The other four resonances correspond to states in ^{11}B whose energies match well with those of the first four states in ^{11}Be: T = 3/2. Several known T = 1/2 states in ^{11}B 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 γrays see Table 11.12 (in PDF or PS) (1967TH05). The τ_{m} for ^{11}B*(6.74) is 10^{+12}_{8} fsec (1969WE07). See also (1973AR1M, 1974AR1K, 1974ST1C) and (1968FOZY; astrophys.).
The "free" neutron scattering cross section, (σbar)_{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 E_{n} = 0.7 to 10 keV and then rises to 2.97 b at E_{n} = 127 keV (1970AS10). Total cross section measurements in the range E_{n} = 10 to 500 keV confirm the broad maximum near E_{n} = 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 E_{n} = 1.9 and 2.8 MeV (1951BO45) and at 4.3 MeV (1961FO07): see Table 11.13 (in PDF or PS). In the range E_{n} = 5.5 to 16 MeV σ_{tot} 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 Rmatrix calculations: the results are shown in Table 11.14 (in PDF or PS). They are consistent with results from ^{10}B(n, n'γ) and ^{7}Li(α, n). Elastic scattering differential cross sections are also reported at E_{n} = 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 γrays has been studied from threshold to E_{n} = 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 ^{10}B states have been measured by (1970NE03: E_{n} = 1.45 to 4.90 MeV, and 14.8 MeV), (1969HO1G: E_{n} = 7.02 and 7.55 MeV) and (1970CO12: E_{n} = 9.72 MeV). See also ^{10}B in (1974AJ01) and (1969RO1F).
The thermal cross section is < 0.2 b (1973MU14). See also ^{9}Be in (1974AJ01) and (1970NE03).
See ^{9}Be in (1974AJ01).
The cross section for reaction (b) has been measured for E_{n} = 1.4 to 8.2 MeV by (1961DA16). Fluctuations are observed at some of the resonant energies in the ^{10}B(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 E_{n} = 10 eV to 200 keV is given by the expression
The cross section for the (n, α_{0}) reaction has been calculated by (1968MA07) from that for the ^{7}Li(α, n) reaction: E_{n} = 30 to 516 keV. The α_{1} cross section has been measured for E_{n} = 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 E_{n} = 30 to 800 keV (relative cross sections for α_{0} and α_{1}) and by (1969AN25) at 14.4 MeV (cross section for formation of α_{0} + α_{1}, α_{2}). (1972HA04) have calculated differential cross sections for α_{0} and α_{1} based on Rmatrix parameters derived from neutron elastic scattering, polarization measurements and (n, α) data. See also (1974HA1W, 1975HA1G; theor.). See also ^{7}Li in (1974AJ01), (1968GI1D, 1968GU1B, 1968ST1D, 1970DE1H, 1972LA1F, 1975FR1B), (1964FO1A; astrophys.) and (1968MO1D, 1968PA1E, 1973FA1M, 1973LI1E; applied).
Angular distributions for proton capture to ^{11}B*(0, 2.15 ± 0.10) have been measured at E_{p} = 185 MeV. The population of ^{11}B*(4.45 + 5.02) and of unresolved higher states is also observed but an attempt to observe T = 3/2 analogue states in ^{11}B and ^{11}N (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 E_{d} = 0.17 to 28 MeV [see (1968AJ02) for a listing of the earlier references] and (1970HU1B: 0.35 MeV; p_{0} → p_{3}, p_{4+5}, p_{6}, p_{7}), (1973CO18: 0.67 to 2.32 MeV; p_{4+5}), (1970PO03: 4.5 to 5.5 MeV; p_{0} → p_{3}) and (1967GO27: 13.6 MeV; p_{0}). The lowest five levels are formed by l_{n} = 1 except for ^{11}B*(2.12) which appears to involve a spinflip process. They are presumed to comprise the set 3/2^{}, 1/2^{}, 5/2^{}, 3/2^{}, 7/2^{} expected as the lowest p^{7} levels (a/K ≈ 4.0). ^{11}B*(9.19, 9.28) [J^{π} = 7/2^{+} and 5/2^{+}, respectively] show strong l = 0 stripping and are ascribed to capture of a 2s neutron by ^{10}B: see (1968AJ02) for a listing of all the relevant references. The probability p_{3/2} for transfer of a neutron with angular momentum 3/2 has been determined for the p_{0} group using vector polarized deuterons with E_{d} = 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 ^{12}C, (1967CO30, 1967SP09, 1973BR24), (1973FO02) and (1969BO1F, 1969DO08, 1970DE35, 1970DO07, 1970DO13; theor.).
At E_{d} = 5.5 MeV, deuteron groups are observed to the ground state of ^{11}B and to states at E_{x} = 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 l_{n} = 1 (1961BA10). See also ^{13}C in (1976AJ04).
Angular distributions have been measured at E_{α} = 56 MeV for the ground state transitions in this, and in the analog (α, t) reactions: the average ratio of the (α, ^{3}He) 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).
Not reported.
See (1968OK06).
The angular distribution has been measured at E(^{18}O) = 20 and 24 MeV (1971KN05). See also (1974SW04).
The angular distribution has been measured at E(^{19}F) = 20 and 24 MeV (1971KN05). See also (1968GA03) and (1970GO1B; theor.).
^{11}Be decays to ^{11}B*(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 αparticles are also observed with a total I_{α} of 3.0%/decay. These αparticles are not observed to be in coincidence with 478 keV γrays [upper limit = 5% for E_{α} > 0.3 MeV], suggesting that they result from the decay of ^{11}B*(9.87) to ^{7}Li_{g.s.} (1971AL07). The halflife of ^{11}Be is 13.81 ± 0.08 sec (1970AL21). See also (1968AJ02) and (1974AL11).
Mean gamma widths of lowlying 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 ^{10}B and ^{10}Be (reactions (a) and (b)) (1971PA10). Absolute measurements of the ^{11}B(γ, all n) cross section from threshold to 28 MeV have been carried out by (1973HU09, 1973HU1D): the cross section exhibits a maximum at E_{γ} = 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, d_{0}) 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 Γ_{γ} and J^{π} 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 chargescattering 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 fm^{2}, suggesting a j  j coupling scheme for ^{11}B_{g.s.} (1966RA29). The quadrupole contribution to the elastic form factor is best accounted for by the undeformed shell model, Q = 3.72 ( ± 20%) fm^{2}, r(r.m.s.) = 2.42 fm (1966IS1A, 1966ST12). The excitation of ^{11}B*(2.1, 4.4, 5.0, 8.6, 8.9) has been studied by (1975KA02: E_{e} = 52 to 90 MeV). (1973FL1A) report the excitation of ^{11}B*(7.30, 9.27) at the same E_{e}. The giant resonance region, centered at ≈ 18 MeV, is characterized by a lack of prominent features except for a pronounced peak at E_{x} = 13.0 ± 0.1 MeV (mixed M1  E2) and a broad transverse group at E_{x} = 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 ^{10}Be in (1974AJ01). See also (1968AJ02), (1971RI1E), (1968GO1J, 1972THZF), (1968JA1D, 1969VI02, 1973DO01, 1973GA19, 1973RO11, 1973SP02; theor.).
Angular distributions of neutrons have been measured at E_{n} = 7.55 MeV (1969HO1G: n_{0} → n_{2}), 9.72 MeV (1970CO12: n_{0} → n_{3}, n_{4+5}) and 14.1 MeV (1970AL08: n_{0} → n_{3}, n_{4+5}, n_{6}). For branching ratios see Table 11.4 (in PDF or PS) (1972NI05). See also ^{12}B, (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 E_{p} = 12 to 21.5 MeV (1972TH1C), 30.3 MeV (1969KA15: p_{0} → p_{2}), 100 MeV (1970HO07: p_{0} → p_{3}), 155 MeV (1968GE04: p_{0} → p_{3}, p_{4+5}) and 185 MeV (1969SU03: p_{0} → p_{2} and p to ^{11}B*(8.56, 8.92)). For an angular correlation experiment see (1970HU01). See also (1968AJ02), (1970TH1F, 1973CA1H), (1969WA11, 1971LO05, 1973KA04; theor.) and ^{12}C. For reaction (b) see ^{10}Be in (1974AJ01). The spectroscopic factors for the (t + ^{8}Be) and (α + ^{7}Li) cluster structures in ^{11}B [as determined from a study of the ^{11}B(p, α)^{8}Be reaction] are ≈ 0.77 and ≈ 0.02, respectively (1972DE01, 1972DE02).
The elastic scattering has been studied at E_{d} = 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 E_{t} = 1.8 and 2.1 MeV (1969HE08, 1969SI12).
The elastic scattering has been studied at E(^{3}He) = 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 ^{11}B*(4.45)). A coupled channel analysis of the 74 MeV results suggests a quadrupole deformation β_{2} = +0.43 or 0.50 for ^{11}B (1974AS06). At E(^{3}He) = 29.8 MeV a number of ^{11}B states are populated, including suggested T = 3/2 states [see Table 11.19 (in PDF or PS)] with E_{x} = 12.51 ± 0.05, 12.98 ± 0.09 and 14.40 ± 0.05 MeV, with Γ_{c.m.} = 260 ± 50, 390 ± 120 and 220 ± 50 keV, respectively. There is a weak indication also of a state at E_{x} = 14.51 MeV (1971WA21). See also (1969AD1C, 1970BA1P, 1970DU07). For reaction (b) see (1972YO02).
Angular distributions have been reported at E_{α} = 28.3 MeV (1965KO1A: α_{0} → α_{3}, α_{4+5}, α_{6}), 28.4 and 29.0 MeV (1968KA24: α_{0}) and 28.5 MeV (1967NA06: α_{0} → α_{3}, α_{4+5}, α_{6}, α_{8}). For reaction (b) see (1969FU09).
The elastic scattering has been measured at E(^{6}Li) = 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(^{11}B) = 28 MeV (1969VO07, 1969VO10), at E(^{12}C) = 15, 17, 20 and 24 MeV (1974BO15), and at E(^{12}C) = 87 MeV (1971LI11). The population of ^{11}B*(2.12, 4.45, 6.79) and of ^{12}C*(0, 4.43) has also been reported: see (1969VO07). See also (1974DA1P) and (DE63Y, 1970AN1D; theor.).
The elastic scattering has been investigated at E(^{14}N) = 41, 77 and 113 MeV (1971LI11).
The elastic scattering has been studied at E(^{16}O) = 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.).
See ^{11}C.
The fraction of transitions to the ground and to excited states of ^{11}B [and to ^{11}C states reached in the (γ, n) reaction] has been measured at E_{bs} = 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 ^{11}C (1970ME17). See also the discussions in (1973DI1C, 1973SP03, 1974DI17) and in ^{12}C. Angular distributions of the p_{0+1} and the p_{2+3+4+5} groups have been measured by (1974FI17: E_{γ} = 60, 80, 100 MeV). See also (1968FR12) and (1970MU1D, 1971BI01, 1973MS01, 1973MS02; theor.).
At E_{e} = 497 MeV the excitation of ^{11}B*(0, 2.1, 5.) has been observed by Auriol et al. (see (1972RA1E)). See also (1967AM1A), ^{12}C and (1968BO1D, 1968CI1B, 1968WA1D, 1969BA1F, 1972BE59, 1974HA14; theor.).
Angular distributions have been measured at E_{n} = 56 MeV for the deuterons to ^{11}B*(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 ^{11}B_{g.s.} and an excited state with J^{π} = 1/2^{+} at E_{x} ≈ 19.5 MeV (ejection of p and sprotons, respectively). High resolution experiments show groups corresponding to ^{11}B*(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 ^{12}C.
Angular distributions of ^{3}He ions have been measured at E_{d} = 20, 24, 28 MeV (1971IN1C; unpublished: to ^{11}B*(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: ^{11}B*(0, 6.74)), 28.5 MeV (1966DE1C: to g.s.), 52 MeV (1968HI01: to ^{11}B*(0, 2.12, 4.45, 5.02, 6.74 + 6.79, 7.29)) and 80 MeV (1974AS04: to ^{11}B*(0, 4.45)). A coupled channels Born approximation analysis gives good agreement with the angular distributions: a positive β_{2} is suggested by the results (1974AS04): see, however, (1974KU17). See also (1969KA1A, 1973WA1E, 1974DI1A) and (1969TA1D, 1973ST16, 1974ST18; theor.).
Angular distributions of the αparticles to ^{11}B*(0, 2.12) have been measured at E_{t} = 1 to 2 MeV (1962GU01), 1.11 to 3.40 MeV (1969ET01 and private communication), 10.1 MeV (1962PU01) and 13 MeV (1965AJ01; also α_{2}, α_{3}). Electromagnetic transitions have been studied by (1968BE30): see Table 11.4 (in PDF or PS) (1968BE30) confirm J = 3/2 for ^{11}B*(5.02). See also (1969AR1B) and (1969NA1C; theor.).
This reaction has been studied at E(^{10}B) = 100 MeV: ^{11}B_{g.s.} is much more strongly excited than ^{11}B*(2.12) (1973YO1C, 1973YO1D). The ratios of the yields ^{11}B_{g.s.}/^{11}C_{g.s.} and ^{11}B*(2.12)/^{11}C*(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(^{12}C) = 114 MeV (1974AN36). See also (1967WI04, 1969BR1G).
See (1966PO1B, 1967BI06, 1967VO1A, 1974AN36). See also (1969BR1D, 1973SC1J) and ^{15}O in (1976AJ04).
At E(^{19}F) = 40, 60 and 68.8 MeV angular distributions involving ^{20}Ne _{g.s.} + ^{11}B_{g.s.}, ^{20}Ne^{*}_{1.63} + ^{11}B_{g.s.} and ^{20}Ne_{g.s.} + ^{11}B^{*}_{2.12} (E = 68.8 MeV only) have been measured by (1972SC03). See also (1969VO1D, 1970VO1F) and (1972BO21; theor.).
Not reported.
At E_{p} = 50.5 MeV, in addition to ^{11}B*(0, 2.12, 4.45, 5.02, 6.74, 8.92), a state is observed at E_{x} = 12.94 ± 0.05 MeV, Γ = 350 ± 50 keV. Comparison of the angular distributions of the ^{3}He and of the tritons [in the analog reaction] at E_{p} = 43.7 and 50.5 MeV lead to the assignments J^{π} = 1/2^{}; T = 3/2 for this state and for ^{11}C*(12.50): the strong proton and the weak αdecay are consistent with this assignment (1968CO26). The T = 3/2 state is also observed at E_{p} = 40 MeV by (1974BE20): E_{x} = 12.91 ± 0.03 MeV, Γ = 260 ± 50 keV. ^{11}B*(12.55, 14.33) reported by (1970GO04) in the ^{10}Be(p, γ)^{11}B reaction are not observed by (1974BE20): see Table 11.19 (in PDF or PS). Angular distributions have been measured to ^{11}B*(0, 2.12, 4.45, 5.02) at E_{p} = 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 E_{d} = 0.41 to 0.81 MeV (1971PU01: α_{0}, α_{1}), 1.0 to 2.7 MeV (1970LI1E: α_{0}, α_{1}), 1.4 MeV (1966KL1A: α_{0}), 3.3 to 4.2 MeV (1963MA24: α_{0}), 6.8 MeV (1968DE26: α_{0} → α_{3}), 11.7 MeV (1969CU08: α_{0} → α_{3}) and 12.1, 13.3 and 14.1 MeV (1970KL04: α_{0} → α_{3}). See also (1968AJ02), (1967SP09, 1968CO04, 1971LI1K) and ^{15}N.
See (1974CH1Q).
Angular distributions of the α_{0} → α_{3} groups have been measured at E_{p} = 18 MeV (1962BR34).
Angular distributions for the α_{0} and α_{1} groups have been measured at E_{n} = 4.9 MeV (1972KI12), 14.1 MeV (1968BA30 [also α_{2+3}], 1968HS03 [also α_{2}, α_{3}, α_{4+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 γray (E_{γ} = 2118 ± 5 keV) is isotropic; that for the 4.4 MeV γray shows a weak anisotropy. Both γrays are Doppler broadened: τ_{m} < 100 fsec [see Table 11.5 (in PDF or PS)] (1972NY02). See also (1971NY03) and ^{15}N in (1976AJ04). At E_{n} = 14.1 and 15.7 MeV various states of ^{11}B with 8.9 < E_{x} < 14.5 MeV appear to be involved in the sequential decay to ^{7}Li. Angular correlation results are consistent with J^{π} = 7/2 and 5/2 for ^{11}B*(9.19, 9.28), respectively (1971SC16).
At E_{α} = 72.5 MeV, the excitation of ^{11}B*(0, 2.12, 4.45, 5.02, 6.74) is reported (1974WO1D).
See (1971BO1V).
