(See 2 [Electromagnetic Transitions in A = 11] (in PDF or PS), 11.18 (in PDF or PS), 11.19 (in PDF or PS) and Energy Level Diagram for 11B and Isobar Diagram)
Q = 40.65 ± 0.26 mb (1970NE05),
B(E2; 3/2- → 1/2-) = 2.6 ± 0.4 e2 ⋅ fm4 (1980FE07).
A 13.7 MeV 7Li beam impinged on a thick 4He gas filled chamber and the spectrum of elastically scattered α particles, measured in a position sensitive ΔE-E Si telescope, was evaluated to determine the 7Li(α, α) excitation function (2011YA02). An array of NaI detectors surrounding the target excluded participation of 7Li*(0.48). States deduced from an R-matrix analysis are presented in 11.20 (in PDF or PS).
At E(6Li) = 2 to 16 MeV, angular distributions have been measured for the proton groups corresponding to the first eight states of 11B (1987DO05) and for p0, p1, p2, p6, p7 and p9 (1990LE05). For the earlier work see (1980AJ01). For excitation functions see 12C. See also (1987DO07).
The total cross section has been measured from threshold to Eα = 5.67 MeV [see also reaction 25]: a broad maximum at Eα ≈ 5.1 MeV (σmax = 40 mb) is observed (1984OL05). The neutron spectrum and neutron-to-γ-ray radiation yield of Li-241Am2O3 and Li-238PuO2 sources are evaluated in (1993VL02). For the earlier work see 11.7 (in PDF or PS) in (1985AJ01). See also (1985CA41; astrophys.).
The elastic scattering and the scattering to 7Li*(0.48) have been studied at many energies up to Eα = 22.5 MeV: see (1975AJ02, 1980AJ01, 1985AJ01). Observed resonances are displayed in 11.22 (in PDF or PS). For α-7Li correlations see (1987PO03).
Angular distributions have been measured for E(7Li) = 3.3 to 5.95 MeV: see (1975AJ02).
For reaction (a), angular distributions have been measured at E(7Li) = 2.10 to 16 MeV. See (1975AJ02) for references. At E(7Li) = 2 to 16 MeV angular distributions and excitation functions for p, t and α cluster transfer were measured and evaluated using a DWBA analysis (2010RO09). While proton transfer was found to be nearly a 100% direct process, the α-particle transfer, to 11B was more complex. On average the 11Bg.s. and states at 11B*(2.12, 4.44, 5.02) were populated 20 to 60 % by direct processes; compound nucleus processes were found to be less than 20%. At E(7Li) = 79.6 MeV transitions are observed to several 11B states; 11Bg.s. is particularly strongly populated (1974CE06).
For reaction (b) at E(7Li) = 50.9 MeV (2003FL02), states at 11B*(11.3, 12.5, 14.3) were observed in the 7Li + α relative energy spectra, and at E(7Li) = 58 MeV (2005CU06) states shown in 11.23 (in PDF or PS) were populated. The observations confirm the T = 1/2 nature of the 12.6 MeV and 14.3 MeV states, and the small Γt/Γα ratio for 11B*(12.6) supports the suggestion of (2004SO28) that this state is the 9/2+ member of the Kπ = 3/2+ cluster band.
At E(9Be) = 55 MeV (2005SO13) and 70 MeV (2004SO19, 2004SO28, 2005SO13) states at 11B*(9.3, 10.2, 10.55, 11.2, (11.4), 11.8, 12.5, (13.0), 13.1, (14.0), 14.35, (17.4) and (18.6)) are observed in reaction (a). It is suggested that these states may have a 2α + t cluster structure. These T = 1/2 states have some overlap with T = 3/2 states and may indicate isospin mixing. The states at Ex = 12.5, 14.35, 17.45 MeV are believed to be IAS of low-lying 11Be states.
For reaction (b), participation of 8Be*(0, 3.04) and 7Li*(4.65, 6.6) is found in the reconstruction of 11B*(13.1, 14.4, 17.5) states from α + α + t coincidences. Also see (2007FR22).
Reaction cross sections have been measured at Ecm = 0.9 to 2.8 MeV (2004MI34), Ecm = 0.6 to 2.7 MeV (2004HA54, 2006IS04), Ecm = 1.05 MeV (2008LA08, 2010LA07), Ecm = 1.25 MeV, Ecm = 1.5 to 7 MeV (2000MI34) and E(8Li) = 10 to 20 MeV (1992BO06). Various 12B resonances are observed. Rates for the reaction path 8Li(α, n)11B(n, γ)12B(β)12C are crucial for computing the formation of A > 12 nuclei in inhomogeneous Big Bang Nucelosynthesis (1992BO06, 1993DE30, 2000MI34, 2004CH22). Early estimates for the 8Li(α, n) reaction rate were based on the inverse reaction, 11B(n, α), see i.e. (1990PA22, 1991PA26); however, such measurements are only sensitive to the n0 contribution to the total cross section. The direct measurements with 8Li beams indicate participation of 11B excited states and a much larger total cross section. Systematic issues are evident when comparing inclusive (8Li, n) and exclusive (8Li, n + 11B) results: see (2006IS04). A novel experiment approached the issue by impinging a 8Li beam on a 4He gas target that was located inside a zero-energy-threshold 4π 3He proportional counter embedded in a polyethylene moderator (2008LA08, 2010LA07). See (2000MI34) for branching ratios to n0 through n9. Also see discussion in (1992RA04, 1993OB01, 1994KU28, 1996DE02, 2003SO22), and see (2011AU01) for a discussion of 11B production in core-collapse supernovae.
The θ = 90° γ0 differential cross section has been measured for Ed = 0.5 to 11.9 MeV: see (1975AJ02). 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. Resonant behavior is observed in the θ = 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 (1974DE01).
The cross section follows the Gamow function for Ed = 70 to 110 keV. 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: see (1975AJ02). Thick target yields for γ-rays have been measured at Ed = 48 to 170 keV: see (1985AJ01). Thick target yields are also reported at Ed = 14.8, 18.0 and 23.0 MeV: see (1980AJ01). Polarization measurements have been carried out at Ed = 0.4 to 5.5 MeV [see (1975AJ02, 1980AJ01)] and at Epol. d = 12.3 MeV: see (1985AJ01). See also 10B in (2004TI06).
Measurements of proton yields have been carried out at Ed ≤ 6.0 MeV for p0 and p1 [see (1975AJ02, 1980AJ01, 1985AJ01)]. The p0 and p1 yields show a resonance at Ed = 750 ± 15 keV [11B*(16.43), Γ ≈ 40 keV] and the p1 yield resonates at 1.85 MeV [11B*(17.33), Γcm ≈ 1.0 MeV] and 2.3 MeV [11B*(17.70), sharp]. See also (1975AJ02, 1985AJ01) for other possible structures. Polarization of the protons has been measured at Ed = 1 to 21 MeV [see (1975AJ02, 1980AJ01, 1985AJ01, 1990AJ01)] and at Epol. d = 2.5 to 3.0 MeV (1995LY03). See also 10Be in (2004TI06).
The yield of α-particles (reaction (b)) has been measured for Ed = 0.3 to 14.43 MeV [see (1975AJ02, 1980AJ01, 1985AJ01)]. The 0.75 MeV resonance, observed in reaction (a), is weakly populated in the α0 yield. The VAP was measured for α0+1 at Ed = 2.0 to 3.0 MeV and compiled for 1.4 to 3.0 MeV (1994LY02); analysis shows influence from 11B*(17.33, 17.43, 17.7, 18.0). For other polarization measurements see references in (1985AJ01, 1990AJ01). Also see 7Li in (2002TI10).
The cross section for reaction (c) has been measured for Ed = 0.15 to 19 MeV: see (1968AJ02, 1975AJ02, 1980AJ01), and for Ed = 3 to 11 MeV (1995AB41). Resonant structures are reported by (1995AB41) near 11B*(18.1, 19.5, 22.4, 24.4). Polarization measurements are reported at Epol. d = 12 and 15 MeV [see (1980AJ01, 1990AJ01)] and at Epol. d = 2.5 to 3.0 MeV (1994LY02). In the analysis of (1994LY02), which included VAPs for Ed = 1.4 to 3.0 MeV, an anomaly near Ed = 2.4 MeV is attributed to a resonance at E(11B) ≈ 17.8 MeV, which could be the IAS to 11Be*(5.25). See also 8Be in (2004TI06).
Excitation functions for elastically scattered deuterons have been measured for Ed = 0.4 to 7.0 MeV and for 12.17 to 14.43 MeV (also d1, d2) [see (1975AJ02, 1980AJ01)]. Polarization measurements have been reported at Epol. d = 6.3 to 15 MeV [see (1975AJ02, 1980AJ01, 1990AJ01)]. See also a 9Be in (1988AJ01).
Angular distributions have been measured at Et = 1.1 to 1.7 MeV (n0, n1, n2, n6, n8, n9): see (1980AJ01).
Observed proton groups are displayed in 11.24 (in PDF or PS). Angular distributions have been obtained at a number of energies in the range E(3He) = 1.0 to 38 MeV [see (1980AJ01, 1985AJ01, 1990AJ01)]. It is suggested that the T = 1/2 strength is strongly fragmented (1982ZW02). See also 12C in (1990AJ01).
Angular distributions have been measured at a number of energies in the range Eα = 23.4 to 30.2 MeV [see (1980AJ01, 1990AJ01)]. The predominant L-transfers are L = 0, 2; 0; 0 for 11B*(0, 2.12, 5.02). The angular distribution to 11B*(4.44) is flat at Eα = 27 MeV. At Eα = 48 MeV, 11B*(16.44, 17.69, 18.0, 19.15) are not excited suggesting that these states are rather pure T = 3/2 states (1982ZW02): also see 9Be(3He, p)11B 11.24 (in PDF or PS).
Angular distributions have been determined for seven α-groups at E(6Li) = 3 to 4 MeV, and at 24 MeV to 11B*(0, 2.12) and to a number of unresolved levels with Ex ≤ 13.2 MeV: see (1968AJ02, 1975AJ02). For the breakup reactions see (1975AJ02).
Angular distributions for elastic and inelastic scattering have been measured at E(11B) = 45 MeV (2003RU02). Distributions for 11B*(2.12, 4.445, 5.020, 6.743 + 6.792, 7.28, 7.978, and 8.560) were analyzed with an emphasis on determining the large angle scattering mechanism which is sensitive to the short range nucleus-nucleus interaction. Deformation parameters were deduced for 9Be and 11B states.
The yield of γ0 has been measured at 90° for Ep = 0.6 to 6.3 MeV. Observed resonances are displayed in 11.25 (in PDF or PS). T = 3/2 assignments are made for the states at Ex = 12.56, 12.91, 14.33 and 15.32 MeV whose energies match those of the first four states of 11Be [compare with the T = 3/2 states reported in 9Be(3He, p)11B - 11.24 (in PDF or PS) and 11.34 (in PDF or PS)]. Several known T = 1/2 states in 11B are not observed in this reaction: see 11.18 (in PDF or PS). Parameters of the 12.56 MeV state are discussed in (2006FO14, 2007BA54).
The reaction cross section has been measured for Ep = 0.89 to 1.93 MeV: the excitation of 11B*(12.56, 12.91) is reported (1986TE1A and G.M. Ter-Akopian, private communication; 1987ERZY). See also (1988DU06; theor.).
Values reported for the thermal capture cross section are inconsistent. The Atlas of Neutron Resonances evaluation gives the value σγ = 305 ± 16 mb (2006MUZX); an earlier evaluation of the thermal capture cross sections reported σγ = 0.5 ± 0.1 b (2003MUZZ). At the same time, the results of the measurements and analysis for the Evaluated Gamma-ray Activation File (EGAF) project deduced σγ = 303 ± 20 mb (2003LI1L), but the value σγ = 390 ± 11 mb was later published by that group (2008FIZZ). The earlier reported values are σγ = 0.29 ± 0.04 b (1986KO19) and 0.5 ± 0.2 (1957BA18, 1973MU14). Reviewing these reported values, we accept the value σγ = 305 ± 16 mb from the Atlas of Neutron Resonances (2006MUZX). The observed capture γ-rays are displayed in 11.26 (in PDF or PS). A compilation of thermal capture data is in (2002RE13).
Coherent neutron scattering lengths and free cross sections were measured to determine the spin-dependent scattering length (1983KO17, 2006MUZX). The coherent scattering length b(10B) = -0.2 ± 0.4 fm (1983KO17) and the total free scattering cross section σ0 = 2.23 ± 0.06 b (1970AS10) are used to deduce the spin state scattering lengths a+ = -3.8 ± 0.4 fm, a- = 4.7 ± 0.4 fm, b+ = -4.2 ± 0.4 fm and b- = 5.2 ± 0.4 fm which implies a vanishing coherent scattering cross section. Therefore neutron scattering on 10B is totally incoherent (1983KO17). 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. For a display of cross sections and a listing of measurements see (1988MCZT).
Total cross section measurements in the range En = 10 to 500 keV show a broad maximum near En = 0.23 MeV, also observed in the (n, α) cross section. At higher energies the total cross section shows broad maxima at En = 1.9, 2.8 and 4.3 MeV: see 11.28 (in PDF or PS). In the range En = 5.5 to 16 MeV σtot is constant at 1.5 b.
Elastic and inelastic cross sections have also been reported at En = 4 to 17 MeV [see (1980AJ01, 1990AJ01)], and at En = 3.0 to 12.0 MeV (1990SA24). Inelastic scattering cross sections for formation of the first five states of 10B have been measured in the range En = 3.0 to 12 MeV (1990SA24); twelve levels in 11B above Ex = 13 MeV were identified. See 11.27 (in PDF or PS) for the R-matrix analysis of (n, n0-5) and (n, nα0+1) data given in (1990SA24). The yield of 0.7 MeV γ-rays has been studied from threshold to En = 5.2 MeV: observed resonances are displayed in 11.28 (in PDF or PS). See 11.13 (in PDF or PS) in (1980AJ01) for an R-matrix analysis of cross section and analyzing power measurements from En = 0.075 to 4.4 MeV, and see (1975AJ02) for an analysis of measurements from En = 1.45 to 14.8 MeV. See also 10B in (1988AJ01).
See (2008MU23) for an analysis of the En < 2 MeV 10B(n, n) International Cross Section Standard: (1996CH33) for an optical model analysis of elastic scattering up to En = 200 MeV: and (2001AB14) for measurements at En ≤ 600 MeV. See (2008GE04) for an analysis on Mott-Schwinger scattering of E = 0 to 25 meV neutrons.
The thermal cross section for reaction (a) is 6.4 ± 0.5 mb (1987LA16); that for reaction (b) is reported as σ = 4.47 ± 0.15 mb (1989CL01: see also for other references) and σ = 7 ± 2 mb (1987KA32). For reaction (a), differential cross sections were measured for En = 70 to 240 MeV (2007SO06); the stretched transition to 10Beg.s. was studied in a DWIA analysis. The cross section for reaction (b) has also been studied for En = 1.4 to 8.2 MeV [see 11.28 (in PDF or PS) and (1968AJ02)] and 3 to 8 MeV (1986QA01). For various breakup processes see (1984TU02). For a display of cross sections and a listing of measurements see (1988MCZT).
The "recommended" value of the thermal isotopic absorption cross section is 3837 ± 9 b (1981MUZQ, 2006MUZX). Also see σ = 3820 ± 135 b (2003MOZU). The k0 factor for prompt 478 keV γ-rays from thermal neutron activation was measured in (2001AC04, 2003CHZX, 2004MA76).
The cross section for this reaction has been measured for En = 4.17 to 6.52 MeV (2002ZH35), En = 1.5 to 5.6 MeV (2005GI03, 2006GI03), En = 4.0 and 5.0 MeV (2008ZH20) and for En = 0.025 eV to 14.8 MeV [see (1975AJ02, 1980AJ01, 1985AJ01)]: for observed and deduced structures see 11.27 (in PDF or PS) and 11.28 (in PDF or PS). A study of the reaction involving polarized thermal neutrons and a polarized 10B target shows that the transition to 7Li*(0.48) proceeds almost totally through the J = 7/2 channel (1986KO19). For a display of cross sections and a listing of measurements see (1988MCZT). For a review see (1986CA28). "Detailed balance" [from 7Li(α, n) measurements] has led to the determination of the 10B(n, α0) cross section from 0 < En ≤ 0.78 MeV: two resonances are inferred at ER = 241 ± 18 and 493 ± 4 keV, with σR = 17 ± 3 and 112 ± 3 mb and Γ = 166 ± 40 and 194 ± 6 keV (1984OL05). Also see (2008LA18) for an indirect determination of the astrophysical S-factor via 2H(10B, pα) at E(10B) = 27 MeV.
The α0/α1 branching for thermal neutrons is (6.723 ± 0.011)% [mean of values listed in (1985AJ01)]. At En = 2 and 24 keV the α0/α1 ratios are (7.05 ± 0.16)% and (7.13 ± 0.15)%, respectively (1979ST03). At En = thermal to 5.5 keV, ratio values are reported near 6.7 ± 0.3 % (2000GO03). The ratio is reported for En = 0.1 keV to 1 MeV (2002HAZP, 2007HA06), En = 0.1 to 2 MeV (2009HA19), En = 20 keV to 1 MeV (1991WE11) and En = 0.2 to 0.4 MeV (1993SC20). Sizeable discrepancies between the data and the ENDF/B-VII library exist above 1 MeV.
Parity violation has been studied using polarized thermal neutrons: the P-odd asymmetries for the transitions to 7Li*(0, 0.48) are < 3.7 × 10-6 (1986ER05) and +(0.0 ± 2.6 (stat.) ± 1.1 (sys.)) × 10-8 (2011VE06), respectively: see also (1983VE10, 1994GL07, 1996VE02, 1999VE03, 2002VEZY, 2003VE10, 2005GI03, 2007NI05), and (1985AJ01) for the earlier work. See also 7Li in (1988AJ01).
The T-odd asymmetry parameter, related to time reversal invariance, is discussed in (2000GA43, 2003BA36, 2007NI05); an upper limit of 3.2 × 10-4 is deduced from analysis of 10B(pol. n, αγ) at thermal energies (2000GA43).
Angular distributions have been obtained at Ep = 168 to 800 MeV to several states of 11B [see (1980AJ01, 1985AJ01)] as have cross sections for π+ production near threshold. At Epol. p = 200 to 260 MeV, angular distributions and analyzing powers have been measured for the groups to 11B*(0, 2.12) (1985ZI04). Angular distributions of pions have been measured at Ep = 209, 247 and 364 MeV (1995BB15).
Reported proton groups are displayed in 11.14 (in PDF or PS) of (1980AJ01). Angular distributions have been studied at energies in the range Ed = 0.17 to 28 MeV [see (1968AJ02, 1975AJ02, 1980AJ01)]. 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, 9.27) [Jπ = 7/2+, 5/2+] 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. At Ed = 15.3 MeV, differential cross sections were measured for (d, p2γ) to obtain the spin-tensor components of the density matrix (2005GA59); neutron stripping appears to be the dominant mechanism. Deformation parameters β2(10B) = -0.55 and β2(11B) = 0.4 were deduced. A survey of ground state neutron spectroscopic parameters is given in (2005NI24, 2005TS03). Other studies of pγ correlations are discussed in reaction 14 of (1968AJ02) and displayed here in 11.19 (in PDF or PS). See also 12C.
Astrophysical S-factors are deduced from measurements at Ed = 60 to 140 keV (1993CE02, 1997YA02, 1997YA08), at Ed = 100 to 300 keV (2004RU10), and at Ed = 120 to 340 keV (2001HO22). At Ed < 3 MeV the p0-p3 reaction cross sections were analyzed to evaluate the impact of the 12C GDR and GQR on the astrophysical rates (2005RU16). At Ed = 900 to 2000 keV angular distributions and differential cross sections were measured for p0-p6, motivated mainly by boron composition depth profiling studies (2007KO69).
11Be decays to many states of 11B (1982MI08): see 11.29 (in PDF or PS) for the observed β- and γ-transitions. 11B*(9.88) decays via α-emission to 7Li*(0, 0.48) with branching ratios (87.4 ± 1.2)% and (12.6 ± 1.2)%, respectively (1981AL03). A study of the βν angular correlation in the first-forbidden decay of 11Be to the Jπ = 1/2- state 11B*(2.12) has been performed; the β-transition is dominated by rank-0 matrix elements and is of interest as a test of meson-exchange effects: see (1982WA18, 1994WA01). See (1992HE12) who propose first forbidden β-decay as a probe of T-odd forces, and see (1993HA29) for discussion on β-decay isospin mixing probabilities and the 11Be nuclear halo.
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)]. Absolute measurements of the 11B(γ, all n) cross section have been carried out from threshold to 35 MeV: the cross section exhibits a main peak at Eγ = 25 to 28 MeV and weak shoulders at 13 and 16 MeV. The integrated cross section up to 35 MeV is 69.1 ± 0.8 MeV ⋅ mb: see (1980AJ01) and (1988DI02). See also (1984AL22). For other structures reported in the (γ, n) and (γ, p) cross sections see (1975AJ02). The yield of 3.37 MeV γ-rays [from 10Be*(3.37), reaction (b)] has been measured for Ebrem = 100 to 800 MeV. See also (1984AL22, 1986AL24). The (γ, d0) cross section peaks at ≈ 19 MeV, lower than it would be expected to if T = 3/2 states were involved. For reaction (d) see (1986AL24). See (1980AJ01, 1985AJ01) for references and for other photonuclear processes.
[See also unpublished result in (1980AJ01).]
Magnetic elastic scattering at θ = 180° shows strong M3 effects: the derived ratio of static M3/M1, 2.9 ± 0.2 fm2, suggests a j-j coupling scheme for 11Bg.s.. The quadrupole contribution to the elastic form factor is best accounted for by the undeformed shell model, Q = 3.72(± 20%) fm2, 〈 r2 〉1/2 = 2.42 fm. See (1980AJ01) for references. A study of the elastic scattering for q = 2.0 to 3.9 fm-1 is reported by (1988HI02): the M3 component is dominant in the elastic form factor for q > 1.5 fm-1. See also (1994AM01, 1994BO04).
The excitation of 11B*(2.1, 4.4, 5.0, 8.6, 8.9) has been studied. 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. At Ee = 121, 186 and 250 MeV form factors (and B(Eλ)↑) are obtained for 11B*(4.4, 6.7, 8.5, 8.9, 13.00 ± 0.15) and the excitation of 11B*(14.50 ± 0.15, 16.7 ± 0.2) is also reported: see (1985AJ01). See also (1994MO19).
The proton matter distribution in 11Bg.s. has a radius of 2.368 ± 0.021 fm, assuming that for 12C to be 2.44 fm. The result is not sensitive to the details of the optical-model calculations (1980BA45: Eπ+ = 38.6 and 47.7 MeV).
Angular distributions have been reported for En = 75 keV to 14.1 MeV [see (1980AJ01, 1985AJ01)] and at En = 8.0 to 13.9 MeV (1982GL02; n0 → n3). Other work is reported for En ≤ 17 MeV (1986MU08; n0). See (1995XI06) for analysis of En = 7.54 to 20 MeV, (2000ZHZR) for En < 20 MeV, and (1996CH33) for En < 200 MeV. A measurement of the total cross section for 11B(n, X) at En ≤ 600 MeV is given in (2001AB14). See an analysis of Mott-Schwinger scattering of En < 25 meV in (2008GE04). See also 12B.
Observed proton groups for reaction (a) are displayed in 11.32 (in PDF or PS). Angular distributions have been measured for Ep = 6 to 185 MeV [see (1980AJ01)], Ep = 0.5 to 3.3 MeV (2001CH78), Ep = 0.6 to 1.2 MeV (2011AM02), Ep = 1.7 to 2.7 MeV (1998MA54), Ep = 10 to 17 MeV (1986MU08), Ep = 392 MeV (2004KA53, 2004KA56) and at Ep = 1 GeV (1985AL16). Spin-isovector M1 strengths are given in (2003HA11) for excitation of the first three states with Epol. p = 150 MeV. Polarization transfer coefficients for p0 and p3 were measured at Ep = 150 MeV (2003HA12). At Ep = 2.2 to 4.2 MeV and θ = 135° to 160°, proton elastic scattering cross sections were measured to evaluate the suitability of the reaction for boron depth profiling (2010KO33). At Ep = 3.2 to 3.6 MeV, thick target γ-ray yields were measured for PIGE analysis (1990BO15). Also see (1998DO16). For reactions (b) and (c) at Ep = 392 MeV see (2005NO13) and at Ep = 1 GeV see (1985BE30, 1985DO16). For pion production see (1988AB05). See also 12C, and (1985AJ01).
Elastic scattering has been studied at Ed = 5.5 and 11.8 MeV: see (1980AJ01). At Ed = 200 MeV, angular distributions were measured for 11B*(2.12, 4.44, 5.05, 6.74, 8.56, (8.92)) (2004KA53, 2007KA17, 2007KA49). Isoscalar M1 spin-flip strengths, B(σ), were derived (2004KA53), and isoscalar monopole and quadrupole strengths were deduced (2007KA17): see 11.33 (in PDF or PS). The large monopole strength for Ex = 8.56 MeV is interpreted as evidence for a developed 2α + t cluster structure. See (2011DE17) for a discussion of the radius of the 11B*(8.56) state, and a comparison with the 12C*(7.65) Hoyle state.
The elastic scattering has been studied at Et = 1.8 and 2.1 MeV: see (1980AJ01).
The elastic scattering has been studied at E(3He) = 8 to 74 MeV: see (1975AJ02, 1980AJ01). At E(3He) = 17.5 and 40 MeV angular distributions have been studied for the 3He ions to 11B*(2.12, 4.44, 5.02, 6.74). T = 3/2 states observed in this reaction are displayed in 11.34 (in PDF or PS). See also (1985AJ01). There is a weak indication of a state at Ex = 14.51 MeV: see (1975AJ02).
Angular distributions have been reported at Eα = 24 to 54.1 MeV [see (1975AJ02, 1980AJ01, 1985AJ01, 1990AJ01)]. A review of α-particle scattering cross sections for Eα = 2 to 8 MeV is given in (1991LE33). Elastic and inelastic scattering were measured at Eα = 40 and 50 MeV (2005BU33); optical model, β2 and β4 deformation parameters were deduced. A DWBA analysis of data taken at Eα = 388 MeV is given in (2010KAZZ). Depth profile studies on boron-doped materials have been carried at Eα = 3.5 to 7.5 MeV (1990MO21) and at Eα = 1.0 to 5.3 MeV (1996LI62, 1996ZH36).
Cluster configuration spectroscopic factors are deduced (1995BO31) at Eα = 27.2 MeV.
The elastic scattering has been studied at E(6Li) = 28 MeV: see (1975AJ02). At E(7Li) = 34 MeV angular distributions have been reported to 11B*(0, 2.12, 4.44, 5.02, 6.74, 7.29, 8.92) (1987CO02, 1987CO16); also see (2005RU17, 2005RU18). At E(11B) = 44 MeV, scattering on a 7Li target populated 11B*(0, 2.12, 4.44, 5.02, 6.74, 7.29, 7.98, 8.56, 8.92) (2005RU18). Deformation parameters were deduced for 7Li and 11B states, and contributions from 1- and 2-step cluster transfers are found to be small in both the elastic and inelastic channels.
The elastic scattering has been studied at E(11B) = 18.8 to 50 MeV and at E(12C) = 15 to 24 MeV and 87 MeV [see (1980AJ01, 1985AJ01)] as well as at E(11B) = 10.4, 12.4 and 14.6 MeV (1985JA01), at Ecm = 25 MeV (1986MA13), at E(11B) = 42.5 to 100 MeV (1985MA10) and at E(12C) = 65 MeV (1985GO1H) [see 12C]. The population of 11B*(2.12, 4.44, 6.79) is reported. For yields, fusion and breakup studies see (1985AJ01) and (1985MA10, 1986MA13). For reaction (b) see (1984DEZX, 1984HAZK).
The elastic scattering in reaction (a) has been studied at E(16O) = 14.5 to 60 MeV and at E(11B) = 41.6, 49.5 and 115 MeV; for references see (1975AJ02, 1980AJ01, 1985AJ01). Elastic and quasi-elastic scattering are reported in (1994AN05: E(16O) = 22 to 64 MeV). Also see (1992KA19).
For reaction (b) see (1994AN05). For reaction (c), elastic and quasi-elastic scattering are reported at Ecm = 18.8 and 19.9 MeV (1992LE04), at E(18O) = 22 to 64 MeV (1994AN05), and at E(11B) = 115 MeV (1980PR09; elastic). Analysis in (1992LE04) evaluated evidence for long-lived orbiting phenomena in the compound system.
The elastic angular distribution has been studied at E(11B) = 115 MeV: see (1985AJ01).
Angular distributions to the ground and to excited states of 11B (and to 11C states reached in the (γ, n) reaction) have been measured at various energies (see 11.35 (in PDF or PS)); the ground state is predominantly populated: see measurements and discussion in (1980AJ01, 1985AJ01, 1990AJ01) and (1986AN25, 1986MC15, 1990SP06, 1990VA07, 1990VA09, 1991IS09, 1993IR01, 1994NI04, 1994ZO01, 1995HA03, 1996RU15, 1997AS01, 1997ZO02, 1998KU23, 1998SO18, 2001ME29). Analog states are populated similarly in the (γ, n) and (γ, p) reactions. Also see (2000DE58).
Bremsstrahlung photons at Eγ = 50 to 70 MeV (tagged) were used to study 12C(γ, pγ')11B; states at 11B*(2.12, 4.45, 5.02, 6.74, 6.79, 7.29) were resolved. The analysis centered on the mechanism for populating the ≈ 7 MeV triplet states (1998KU23). The relative population of 11B*(6.8) is much greater than that reported in (e, ep) (1988SH08). The role of different reaction mechanisms, including quasi-deuteron knockout, is investigated in (1990VA07, 1992RY02, 1992VA01, 1993HA12, 1993IR01, 1994NI04, 1995MO18, 1996AS02, 1996JO15, 1996RU15, 1997AS01, 1997JO07, 2000LE38, 2002ME17, 2005KA54).
Reactions in the "Delta" resonance region are discussed in (1992BA57, 1992GL04, 1995CR04, 1997JO07, 2000GL08, 2001MA31, 2002ME17, 2006AN22). In this region peaks corresponding to removal of s-shell and p-shell protons are observed in the missing mass spectrum, and quasi-free photo pion production is an important reaction mechanism. Evidence for η-mesic 11B atoms is claimed in (1999SO18, 2000SO19, 2002BA21); also see (1995LE26, 1999LE35, 1999TR09, 2003HE18, 2005NA17, 2005NA25, 2005NA35, 2006NA34, 2008JI06).
Neutrino induced proton knockout reactions on 12C are discussed in (1995UM02, 1995UM03, 2003KO50, 2008MA21, 2008ME03). Sensitivity to the strange quark content of the nucleon is given in (1993GA20, 2004ME18, 2004VA09, 2006LA13, 2006ME17, 2006ME24, 2006MA67). Enhancement of 11B production in supernovae explosions is discussed in (2006SU15, 2007SU08).
Measurements reported at Ee = 21 MeV to 14.5 GeV are listed in 11.36 (in PDF or PS). Levels at 11B*(0, 2.12, 4.44, 5.02, 6.74, 6.79, 7.28) are populated; see discussion in (1985VA16, 1988VA09, 1988VA21, 1990DE16, 1992BO10, 1994CA08, 1994IR01, 1994TA11, 1996KE03). 11B*(0, 2.12, 5.02) are populated by l = 1 knockout (1988VA09). The relative population of 11B*(6.8) is much less than that reported in (γ, p) (1988SH08). A high-resolution measurement reported in (1988VA21) observed weak transitions to 8.61 ± 0.05, 9.820 ± 0.025 MeV and to a broad structure at 11.5 MeV. l = 0 and 1 are suggested for the structures at 9.8 and 11.5 MeV. A structure at ≈ 12 MeV is reported in (1996KE03). One-third to one-half of the sum-rule strength predicted by the independent-particle shell model is observed (1988VA09). Weak population of 11B*(4.44) by (1992BO10) is interpreted as arising almost completely from two-step processes.
Spectroscopic factors for 1s and 1p shell single-particle knockout reactions are discussed in (1990CA14, 1990DE16, 1990WE06, 1991WE10, 1991WE16, 1994IR01, 1994IR02, 1995BL10, 1995KE03, 1998WO01, 1999DO30, 1999RY06, 2000DU12, 2000LA23, 2002MA12). Effects such as transparency of the nuclear medium have been studied by (1990FR11, 1992BE23, 1992FR17, 1992GA02, 1992JE03, 1992PA03, 1993LO01, 1993NI11, 1994FR12, 1994FR16, 1994GR05, 1994IR02, 1994MA23, 1994NI05, 1995FR04, 1996KE14, 1996NI13, 1997IW03, 1999RY06, 2000DU12, 2000LA23, 2001FR06, 2002DE11, 2002GA43, 2002ME17, 2003DU23, 2003RY02, 2004LA13, 2004BA99, 2005RO38, 2006RO37). Discussion on other final state interactions is given in (1991CA09, 1994IR02, 1994JE04, 1994RY04, 1995BI07, 1995BI19, 1995NI02, 1996BI01, 1996BI21, 1996JE04, 1999KE04, 2002DE07, 2004BA99, 2004BB15, 2005BA23, 2007PI05), and discussion on the reaction mechanism influence is found in (1990LO09, 1991VA05, 1992DR02, 1993CI05, 1993OF01, 1994IR01, 1994RY03, 1994TA11, 1994WE06, 1999MO02, 2002ME17, 2004FR27, 2004MU29, 2004RO35, 2004TA18, 2011RY03). See also (1993KE02, 1994BI05, 1994VE08, 1994WA19, 1995RY02, 1997BI06, 1997GI13, 1998HO20, 2000DE38, 2000UD01, 2005KE04).
The production of 11B in astrophysical sites with large densities of high-energy electrons is discussed by (1983HO15).
At Eπ+ = 100 to 200 MeV the reaction proceeds primarily to 11Bg.s.. At Eπ = 200 MeV the ratios for σn/σp for the first excited states in 11C/11B(Jπ = 1/2-1) are 1.4 ± 0.2 for π- and 1/1.8 ± 0.2 for π+. At Eπ+ = 60 to 300 MeV 11B*(4.44) [Jπ = 5/2-] is strongly populated as is the analog state in the mirror reaction: see (1980AJ01, 1985AJ01) for references. At Eπ± = 220 MeV the quasi-elastic nature of the scattering has been studied by (1984FA11). The proton Fermi-momentum distributions were analyzed at Eπ- = 0.7, 0.9 and 1.25 GeV/c (2000AB25). See also the studies by (1984ZI1B, 1987HU02, 1991BE43), 12C.
An overview of 12C(p, 2p) measurements is given in 11.37 (in PDF or PS). At Ep = 98.7 MeV groups are observed to 11B*(0, 2.12, 4.44, 5.02, 6.79); DWIA lead to relative spectroscopic factors of 2.0, 0.37, 0.15, 1.08, 0.25 for these states. No evidence is seen for multistep reaction processes which would be necessary to populate 11B*(4.44, 6.74): see (1979DE35). At Ep = 392 MeV (2003YO01) states at Ex ≈ 8.5 and ≈ 10 MeV are also observed in addition to the s-hole state in 11B, which is split into three different components with Ex = 16.1 ± 0.1 MeV (Γ = 5.3 ± 0.3 MeV), Ex = 21.9 ± 0.2 MeV (Γ = 8.1 ± 0.2 MeV) and Ex = 28.7 ± 0.7 MeV (Γ = 9.7 ± 2.5 MeV); also see (2001YA08, 2004YA20, 2004YO06, 2004YO08); see additional discussion on knockout spectroscopic factors in (2002BR26, 2011SI01).
At Ep = 1 GeV the separation energy between 6 and 14 MeV broad 1p3/2 and 1s1/2 groups is 18 MeV (1985BE30, 1985DO16); also see (1967GO01, 1969JA05, 1970SI01, 1971LA16, 1976BH02, 2004AN01, 2008KO12, 2008NO01; exp.) and (1990LO18, 1995GA46, 2003TA03, 2006HI15; theor.). Initial and finial state effects, such as color transparency and nuclear modifications to the NN interaction are discussed in (1966TY01, 1978KO30, 1979JA20, 1988CO02, 1989CO17, 1989PI12, 1997HA15, 1998MA67, 1998NO04, 1999AC03, 1999CA11, 1999CA15, 2000NO03, 2003TA03, 2004AC08; exp.) and (1992LE03, 1994FR12, 1994FR16, 1994KO21, 1997GA16, 2000ST17, 2002DI04, 2004AC08, 2006DA15, 2006VA08, 2007DA19, 2007RY02, 2009CO10; theor.).
Measurements were performed at Ep = 223 MeV (1992CO04) and Ep = 370 and 500 MeV (1998BE38). Population of 11B*(0, 2.12, 5.02) and continuum excitations near 20 MeV, interpreted as 1s1/2 hole excitations, were observed (1998BE38); spectroscopic factors were also deduced.
Angular distributions of 3He ions have been measured for Ed = 20 to 80 MeV and spectroscopic factors have been derived for 11B*(0, 2.12, 5.02): see references in (1975AJ02, 1980AJ01, 1985AJ01). The 12B spin dipole resonance is studied via 12C(d, 2He + n) at Ed = 171 MeV (2007DE28). Also see (2001KR01).
Angular distributions have been measured at Et = 33 MeV (1987FO21, 1991PI09) and 38 MeV (1988SI08) to 11B*(0, 2.12, 4.44, 5.02, 6.74, 7.29, 7.98, 8.56); spectroscopic factors are deduced. As expected, the Jπ = 5/2- and 7/2- states 11B*(4.44, 6.74) are populated by two-step processes. The best Jπ value for 11B*(8.56) is 3/2- but this assumes some direct population which may not be the case. For the earlier work at Et = 1 to 3.4, 10.1 and 13 MeV see (1975AJ02).
The 7Lig.s. angular distribution was measured for reaction (a) at E(6He) = 36.4 MeV. A DWBA analysis reproduces the data (2009LI27).
Peaks corresponding to 11B*(9.3 ± 0.1 and 10.3 ± 0.1 MeV) are observed in the kinematic energy spectrum of 7Lig.s. + α particles following 12C + 10Be reactions at E(10Be) = 302 MeV (2004AH02, 2004AH06). The measurement could not resolve possible participation of 7Li*(0.48).
Angular distributions for elastic and inelastic scattering are reported for E(11B) = 49 MeV 11B*(0, 2.12, 4.45 + 12C(2+), 5.02) (2001RU14, 2003ME36), Ecm = 15 to 40 MeV 11B*(0, 2.12, 4.45) (1991JA09), and E(11B) = 344.5 MeV 11B*(0, 4.45) (1992JA12). Optical model parameters and spectroscopic factors are deduced. Quadrupole deformation parameters of δ2 = 1.0 and 0.8 fm are deduced for 11B*(0, 5.02), respectively (2003ME36).
For reaction (b) at E(11B) = 87 MeV, 11B*(9.19, 9.27, 10.27, 10.61) states were observed at Erel = 527 ± 10 keV, 604 ± 10 keV, 1610 ± 14 keV and 1948 ± 7 keV with measured widths of Γ = 30 ± 11, 37 ± 9, 337 ± 44 and 83 ± 22 keV, respectively (1994WO02). The broad widths of the first two levels are explained with the ≈ 41 keV energy resolution.
At E(12C) = 344.5 MeV angular distributions and spectroscopic factors involving 11B*(0, 2.12) are reported in (1992JA10). Angular distributions involving 11Bg.s. are reported in (1979FU04: E(12C) = 93.8 MeV) and (1974AN36: E(12C) = 114 MeV). See also (1995HO02).
At E(19F) = 40, 60 and 68.8 MeV angular distributions involving 11B*(0, 2.12) and 20Ne*(0, 1.63) have been measured: see (1980AJ01).
At Ep = 50.5 MeV, in addition to 11B*(0, 2.12, 4.44, 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 [to the analog state] 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: see 11.34 (in PDF or PS). Angular distributions have been measured at Ep = 26.9 to 49.6 MeV involving the above states except for 11B*(8.92) and at Epol. p = 65 MeV (to 11B*(0, 2.12)): see (1975AJ02, 1980AJ01, 1985AJ01). See also 14N in (1986AJ01).
Observed α groups are displayed in 11.32 (in PDF or PS). Angular distributions are reported at Ed = 150 to 350 keV (1993MA45), Ed = 180 to 350 keV (1998NA38), Ed = 0.5 to 1.65 MeV (2007CO01), Ed = 15.3 MeV (2009GA19, 2010GA05), and Ed = 0.41 to 14.1 MeV; see references in (1975AJ02).
At Ed = 15.3 MeV analysis of the angular distributions indicates the 4.4 MeV Jπ = 5/2- state is mainly formed by deuteron pickup, while both deuteron pickup and 9Be cluster-exchange are important for 11B*(0, 2.12, 5.02) (2009GA19). In (2010GA05) the measurements were extended to include double differential cross sections for detecting γ+α coincidences. The angular dependences of the even components of density matrix spin tensors, magnetic sublevel populations, and components of multipole moment orientation tensors of the 11B nucleus were obtained and analyzed for 11B*(4.45).
Scattering distributions for 11B*(0, 2.125, 4.445, 5.020, 6.743 + 6.792, 7.286, 7.978, 8.560) and other 13C states were measured at E(11B) = 45 MeV (2003ME13). The mechanism for anomalous large angle scattering was evaluated in Optical Model and Coupled Channels analyses.
Observed states are displayed in 11.32 (in PDF or PS) (1985AR03). It is suggested 11B*(12.92, 15.29, 16.50, 19.07) are T = 3/2, negative-parity states. Spectroscopic factors have also been derived (1985AR03).
At E(11B) = 45 MeV 11B*(0, 2.12, 4.4, 5.02, 6.74 + 6.79, 7.28, 7.97, 8.56) are observed in the scattering reactions (2005ME05).
Angular distributions have been measured for En = 4.9 to 18.8 MeV [see (1975AJ02, 1980AJ01, 1985AJ01)], at En = 1.7 to 7 MeV (2011KHZW), at En = 5.46 to 7.2 MeV (2006KH12; α0-3), and at En = 12.2, 14.1 and 18.0 MeV (1986RU1B; α0, α1). At En = 14.1 and 15.7 MeV various states of 11B with 8.9 < E x < 14.5 MeV appear to be involved in the sequential decay to 7Li. Angular correlation results are consistent with J = 7/2 and 5/2 for 11B*(9.19, 9.27) respectively: see (1975AJ02). In (2006KH12) a comparison of the cross section with the ENDF/B VI values is given, and the impact of 14N in nuclear reactors is discussed.
See (1986VDZY; Ep = 50 MeV).
At Ed = 80 MeV angular distributions have been measured to 11B* (0, 2.12, 4.44 + 5.02, 6.74 + 6.79 + 7.29): see (1980AJ01).
Coulomb excitation of 11B*(2.2) is discussed in (2007BE54).