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GENERAL: See also (1985AJ01), 2 [Electromagnetic Transitions in A = 11-12] (in PDF or PS), 12.2 [Table of Energy Levels] (in PDF or PS).

Model calculations: (1988WO04).

Special states: (1984KA1H, 1986XU02).

Astrophysical questions: (1988AP1A).

Applications: (1988NO1C).

Complex reactions involving ¹²B: (1984HO23, 1984TA1K, 1985JA18, 1985NO1E, 1985PO11, 1985TA09, 1986AV1B, 1986BI1A, 1986CS1A, 1986GA1P, 1986ME06, 1986PO06, 1986UT01, 1986WE1C, 1986XU02, 1987AN1A, 1987BA38, 1987BA1T, 1987EL14, 1987GE1B, 1987JA06, 1987LY04, 1987PE1B, 1987PO23, 1987SA25, 1987VI02, 1987YA16, 1988AU1A, 1988CA06, 1988FO03, 1988KI05, 1988KI06, 1988RU01, 1988SA19, 1988TA1N, 1989DE05, 1989SA10, 1989SE03, 1989ST1G, 1989YO02).

Polarization of ¹²B: (1984KO1A, 1984KU11, 1984TA1M, 1985TA09, 1986AU1E, 1986KU05, 1986NO1C, 1986TA13, 1987AU1D, 1987CO1L, 1987FU13, 1988NO1C).

Muon and neutrino capture and reactions (See also reaction 19.): (1984KU11, 1985GR1A, 1986KU05, 1987BR1L, 1987FU13, 1987MI17, 1988BR24, 1988FU08, 1988MI11, 1988MI20, 1989GM1A).

Pion and kaon capture and reactions (See also reactions 18, 20, and 21.): (1983AS01, 1984AS05, 1984ER06, 1984KA31, 1984MA1U, 1985DO1G, 1985SA06, 1986DI07, 1986SU18, 1988HA12, 1989MR01).

Hypernuclei: (1983SH1E, 1984CH1G, 1984CO1L, 1984MA1U, 1984SH1J, 1984ZH1B, 1985AH1A, 1985CO1H, 1985CO14, 1985DO1G, 1985YA1F, 1986AN1R, 1986BE1P, 1986CO1U, 1986DA1B, 1986FE1A, 1986HA39, 1986KO1A, 1986MA1C, 1986RO25, 1987BE1S, 1987MA08, 1987MA2A, 1987MI38, 1987PO1H, 1988MO1L, 1988RO11, 1988TA29, 1989MR01).

Antinucleon interactions: (1986AU1D).

Other topics: (1984KA1H, 1985AN28, 1986YA1F).

Ground-state properties of ¹²B: (1985AN28, 1986GL1A, 1987VA26, 1988VA03, 1988WO04).

Interaction cross sections at 790 MeV/A by ¹²B ions with Be, C, and Al are reported by (1988TA10). The interaction radius and the r.m.s. radius for the nucleon distribution in ¹²B have also been derived (1988TA10). See also (1989SA10).

¹²B*(3.39) has been produced in the interaction of a 490 MeV ¹⁴N beam with Ag: its 19 keV neutron decay to ¹¹B_g.s. has been observed (1989DE05).

1. 12B(β-)12C

Qm = 13.370

The half-life of ¹²B is 20.20 ± 0.02 ms (1978AL01). See also (1988SA04). The decay is complex. ¹²B decays to ¹²C*(0, 4.4, 7.7, 10.3): see 12.14 (in PDF or PS). The transitions to ¹²C*(0, 4.4) are allowed; hence the J^π of ¹²B(g.s.) is 1⁺. The β-momentum spectrum has recently been measured by (1987NA08). For measurements of the angular distribution functions from oriented ¹²B nuclei see, for instance (1986MI1P, 1986MI1T, 1987MI1P). See also the "Polarization" section in (1985AJ01), (1986CU01, 1986RO27, 1987MI20), (1985GR1A, 1985MI1A), (1985BA2L, 1987RO03; applied) and (1984DU1E, 1984TA1M, 1985MO13, 1986KE1A, 1986KO2C, 1986TO1A, 1987DR1A, 1987KE1B, 1987SA1N, 1988AL1E, 1988SA12, 1989SA1H; theor.).

2. (a) 6Li(7Li, p)12B	Qm = 8.334
(b) 7Li(7Li, d)12B	Qm = 3.309

Eleven groups of protons (reaction (a)) are reported to known states of ¹²B. Angular distributions have been measured at E(⁶Li) = 3.5 to 5.95 MeV. The distributions are generally featureless. Angular distributions for d₀, d₁, d₂, d₃₊₄ have been measured at E(⁷Li) = 2.10 to 5.75 MeV. See (1975AJ02) for references. See also (1984KO25).

3. (a) 9Be(t, n)11B	Qm = 9.5580	Eb = 12.928
(b) 9Be(t, p) 11Be	Qm = -1.165
(c) 9Be(t, d)10Be	Qm = 0.5547
(d) 9Be(t, t)9Be
(e) 9Be(t, α)8Li	Qm = 2.9271
(f) 9Be(t, 6He)6Li	Qm = -5.3807

Thirteen resonances have been reported in reaction (a) corresponding to 13.6 < E_x < 14.7 MeV: see 12.3 (in PDF or PS) in (1975AJ02). The yield of 2.12 MeV γ-rays has been measured for E_t = 1.5 to 3.3 MeV and E(⁹Be) = 10 to 16 MeV: no resonances are observed. This is also the case for the yields of 0.32 MeV (reaction (b)), 0.98 MeV (reaction (e)) and 0.48 MeV γ-rays (from the (t, αn) reaction). Elastically scattered tritons have been studied for E_t = 0.60 to 2.1 MeV and E_{pol. t} = 15 and 17 MeV (also A_y). The yields of α₀ and α₁ have also been reported for E_t = 0.52 to 1.70 MeV: see (1975AJ02). The analyzing powers of the reactions leading to ⁶He_g.s. and ⁶Li*(0, 3.56) have been measured at E _{pol. t} = 17 MeV. For references see (1985AJ01). See also (1988AJ01).

4. 9Be(α, p)12B

Qm = -6.886

See unpublished work in (1985AJ01). See also (1986AU1E).

5. 9Be(6Li, 3He)12B

Qm = -2.8674

At E(⁶Li) = 32 MeV ¹²B*(0, 0.95, 1.67, 3.38, 3.76) and some unresolved states are populated (1986AS02).

6. 9Be(7Li, α)12B

Qm = 10.460

Observed α-particle groups are displayed in 12.3 (in PDF or PS). Angular distributions have been measured at E(⁷Li) = 3.3 to 6.2 MeV, at 20 MeV and at 30.3 MeV: see (1975AJ02, 1980AJ01). At E(⁷Li) = 20 MeV angular distributions to the first seven states are rather featureless and have approximate symmetry about 90°. The integrated cross sections go as 2J_f+1 consistent with a compound nucleus mechanism for the transitions populating the low-lying states of ¹²B. It is suggested that the sharp states of ¹²B at high excitation energies correspond to states of high angular momenta with cluster configurations.

7. (a) 10Be(d, p)11Be	Qm = -1.720	Eb = 12.373
(b) 10Be(d, α)8Li	Qm = 2.3724

The cross sections for production of ⁸Li (reaction (b)) and of ¹¹Be (reaction (a)) have been measured for E_d = 0.67 to 3.0 MeV and 2.3 to 12 MeV, respectively: the yields for both reactions vary smoothly with energy. No resonances are observed: see (1975AJ02).

8. 10B(t, p)12B

Qm = 6.342

Observed excited states are displayed in 12.3 (in PDF or PS). Angular distributions have been studied at E_t = 10 and 23 MeV: see (1980AJ01). See also (1982CI1B; theor.).

9. 11B(n, γ)12B

Qm = 3.370

The thermal-neutron capture cross section is 5.5 ± 3.3 mb [see (1981MUZQ)]. The capture cross section shows resonances at E_n = 20.8 ± 0.5 keV and at 0.43, 1.03, 1.28 and 1.78 MeV, with Γ_γ = 25 ± 8 meV and 0.3, 0.3, 0.2 and 0.9 eV (± 50%): see 12.4 (in PDF or PS) and (1968AJ02). For a summary and the ENDF projections see (1988MCZT). See also (1985BA2L; applied) and (1988MA1U; astrophysics).

10. 11B(n, n) 11B

Qm = 3.370

The thermal (bound) scattering cross section is 3.9 ± 0.2 b. The scatttering amplitude (bound) is a= 6.65 ± 0.04 fm, σ(free) = 4.84 ± 0.04 b (1983KO17). Parameters of observed resonances are shown in 12.4 (in PDF or PS). See also (1981MUZQ). For a summary and the ENDF projections see (1988MCZT). See also (1982GL02). For differential cross sections see ¹¹B. Total cross-section measurements have been reported for E_n = 0.3 to 18.0 MeV: see (1968AJ02, 1980AJ01, 1985AJ01). Polarization measurements have been studied at E_n = 75 keV to 2.2 MeV [see (1980AJ01)] and at E_{pol. n} = 10 to 17 MeV (1985WA1P, 1986MU08; n₀; prelim.).

Results from the most recent R-matrix analysis are displayed in 12.4 (in PDF or PS) (1983KO03). For a discussion of the earlier work see (1980AJ01). See also (1986BAYL, 1986DR10), (1985BO1C) and (1988HAZT; theor.).

11. (a) 11B(n, p)11Be	Qm = -10.7234	Eb = 3.370
(b) 11B(n, d)10Be	Qm = -9.0033
(c) 11B(n, t)9Be	Qm = -9.5580
(d) 11B(n, α)8Li	Qm = -6.6309

The cross section for reaction (a) has been measured for E_n = 14.7 to 16.9 MeV and that for reaction (b) has been investigated for E_n = 12.6 to 20.0 MeV and at 25 and 38 MeV: see (1975AJ02). A study of reaction (d) is reported at E_n = 14.4 MeV: see (1985AJ01). For a summary and the ENDF projections see (1988MCZT). See also (1985FO1D), (1986WI1B; applied) and (1985BO1D).

12. 11B(p, π+)12B

Qm = -136.981

The cross section for π⁺ production near threshold has been measured. At E_p = 200 MeV ¹²B*(0, 0.95, 1.67, 2.62, 3.39, 3.76, 4.30 + 4.52, 5.00, 5.61) are reported: see (1985AJ01). See also the "General" section here.

13. 11B(d, p )12B

Qm = 1.145

Observed proton groups and γ-rays are displayed in 12.5 (in PDF or PS). The J^π assignments for ¹²B*(0.95, 1.67) are derived as follows [see (1968AJ02) for a listing of earlier references]: 0.95 MeV: l_n = 1 leads to J^π = 0⁺, 1⁺, 2⁺ or 3⁺. The γ-radiation is anisotropic and therefore J ≠ 0. τ_m is too short for pure E2 and hence J ≠ 3, which is confirmed by studies of the polarization of γ₁. The results are consistent with J^π = 1⁺ or 2⁺. The latter is fixed by γγ-correlations in the cascade 1.67 ---> 0.95 ---> g.s. The mixing ratio δ = -0.08 ± 0.06. 1.67 MeV: l_n = 0 and therefore J^π = 1^- or 2^-. The state decays primarily to ¹²B(g.s.). Gamma-gamma correlations lead to J^π = 2^-. An assignment of 1^- to ¹²B*(2.62) is made in a similar manner.

See 12.12 (in PDF or PS) in (1980AJ01) for a comparison of the properties of the first seven T = 1 states in ¹²B and in ¹²C.

14. 11B(6Li, 5Li)12B

Qm = -2.30

See (1984KO25).

15. 11B(7Li, 6Li)12B

Qm = -3.880

At E(⁷Li) = 34 MeV angular distributions have been studied to ¹²B*(0, 0.95, 1.67, 2.62 + 2.72, 3.39, 4.52, 5.61 + 5.73) (1987CO16) [see for spectroscopic factors].

16. 11B(9Be, 8Be)12B

Qm = 1.705

See (1984DA17, 1986CU02).

17. 12Be(β-)12B

Qm = 11.708

See ¹²Be.

18. (a) 12C (γ, π+)12B	Qm = -152.938
(b) 12C(e, eπ+)12B	Qm = -152.938

Using monoenergetic photons with E_γ = 210 to 381 MeV (1982AR06) have measured the total cross section for π⁺ emission and the spectra of the positive pions. The latter show the influence of quasi-free pion production and FSI processes. At E_e = 195 to 205 MeV the π⁺ energy distributions show contributions from ¹²B*(0, 0.95, ≈ 4.5, 7.0): see (1986SH14, 1988SH36) and (1985AJ01). The 2^- and 4^- states at E_x ≈ 4.5 MeV have been compared with their isobaric analogs in ¹²C at E_x ≈ 19.5 MeV. At E_e = 400 MeV π⁺ with E_π = 32 MeV have been studied: double differential cross sections are obtained for the transitions to ¹²B*(0, 0.95, 1.67), and single differential cross sections to ¹²B*(0, 0.95). The cross section (at θ = 54°) is the same whether virtual or real photons are used in producing the pions. At E_γ = 176 - 187 MeV the giant resonance region as well as some lower groups have been studied by (1987MIZZ, 1987MI1O; prelim.). See also (1988ADZN).

19. 12C(μ-, ν)12B

Qm = 92.290

Observations of γ-transitions have led to the determination of the capture rates to ¹²B*(0, 0.95, 1.67, 2.62) [J^π = 1⁺, 2⁺, 2^-, 1^-]: see (1985AJ01). The ratio of the polarization of ¹²B_g.s., P_av, and of the longitudinal polarization leads to a neutrino helicity h_ν = -1.08 ± 0.11, in agreement with the partial conservation of axial-vector current (PCAC) hypothesis: see (1985AJ01). The polarization of ¹²B has also been studied recently by (1984KU20): P_av is deduced to be 0.462 ± 0.053 which yields a ratio of the induced pseudoscalar to the axial vector coupling constant in the hadronic weak current, g_p/g_a = 10.1^+2.4_-2.6 which is consistent with the prediction of ≈ 7 from PCAC (1984KU20). See also the "General" section here and (1988DO05).

20. 12C(π-, γ)12B

Qm = 126.199

The photon spectrum from stopped pions is dominated by peaks corresponding to ¹²B*(0, 4.4, 7.9), and branching ratios have been obtained for these and other transitions. That to ¹²B_g.s. is (6.22 ± 0.35)% (absolute branching ratio per stopped pion) (1986PE05). For the earlier work see (1980AJ01).

21. 12C(π-, π0)12B

Qm = -8.765

See (1987CL02) for a study of delta production at E_π^- = 475 MeV. See also (1989BRZX).

22. 12C(n, p)12B

Qm = -12.587

At E_n = 59.6 MeV the angular distribution of the p₀ group is reported. Broad (unresolved) structures are also observed with E_x < 10 MeV: see (1985AJ01). The 0° differential cross section to ¹²B_g.s. at E_n = 198 MeV has been measured. Its ratio to that for the H(n, p) reaction, R, is 0.180 ± 0.006 (1988JA01). The angular distribution to ¹²B*(4.52) [u?] is reported at E_n = 300 MeV (1987WAZY, 1989POZY; prelim.). See also (1985FO1C, 1985FR07, 1985SOZX, 1986DO12, 1986SOZY, 1987FR16, 1987HE24, 1987VE08, 1988RAZX, 1989SOZY) and (1985BR1G, 1986ALZJ, 1986FO1E, 1986VO1G, 1987BR32, 1987HE22, 1988HA1K).

23. 12C(d, 2p)12B

Qm = -14.812

Angular distributions are reported at E_d = 55 and 99.2 MeV to ¹²B*(0, 4.5(u)) [and, at the lower energy to ¹²B*(0.95)] [see (1985AJ01)] and at E_d = 70 MeV (1986MO27, 1988MO11; to ¹²B*(0, 4.5(u)); also VAP, TAP) [¹²B*(0.95, 8.2) are also populated]. See also (1986EL1C, 1987EL14).

24. 12C(7Li, 7Be)12B

Qm = -14.231

At E(⁷Li) = 150 MeV, giant resonances at E_x = 21.8 ± 0.4 (Γ = 1.3 ± 0.4) and 23.9 ± 1.0 (Γ = 6.0 ± 1.0) MeV, with J^π = 3^- and 1^-, respectively, have been reported by (1987NA16). For the earlier work see (1985AJ01). See also (1983PU01), (1987COZZ) and (1984BA53; theor.).

25. 12C(12C, 12N)12B

Qm = -30.708

At E(¹²C) = 35 MeV/A forward-angle differential cross sections have been measured for the groups to ¹²B*(0, 0.95, 1.67, 4.5[u]). A broad peak E_x = 7.8 MeV is also populated (1986WI05). The groups to ¹²B*(4.5)[u] dominate the spectra at this energy (1986WI05) and at 30 MeV/A (1986VO1J). For preliminary work at 70 MeV/A see (1988BO1R, 1989ANZZ). For a recent review of the excitation of the Δ-resonance see (1988RO1H). See also (1986BA16, 1988ANZY), (1986RO1Q, 1987AU04, 1987EL14, 1988AN06, 1988RO17, 1988VO06) and (1986BA1D, 1986DE34, 1986DU1N, 1986LE1N, 1988LE12, 1989LE03; theor.).

26. 12C(13C, 13N)12B

Qm = -15.590

Differential cross sections at θ = 1.8° are reported at E(¹³C) = 30 MeV/A for the groups to ¹²B*(0, 0.95, 4.5[u]) and to structures at E_x ≈ 5.5, 7.8, 10.1 and 18.2 MeV (1987AD07). See also (1988VO08). ¹²B*(1.67, 2.62, 3.38) are also populated (1988VO06; 0°; 29.2 MeV/A). At E(¹³C) = 50 MeV/A the GDR peak is located at 7.7 ± 0.1 MeV (Γ_c.m. = 1.9 ± 0.1 MeV). Forward-angle differential cross sections have been measured also for ¹²B*(0, 0.95) (1989BE50) [and M. Buenerd, private communication]. See also (1986VO02, 1989VO1D).

27. 13C(d, 3He)12B

Qm = -12.040

Angular distributions have been measured for the transitions to ¹²B*(0, 0.95) at E_d = 24.1 to 29 and at 52 MeV. Distributions to ¹²B*(2.72, 3.76, 5.00) have been reported at E_d = 52 MeV: see (1980AJ01). The spectroscopic factors for ¹²B*(0, 0.95) are S = 1.1 ± 0.2 and 2.0 ± 0.5. C²S = 1.09 [assuming 1p_3/2], 2.17, 0.14, 0.07, 0.22 [assuming 1p_1/2] for ¹²B*(0, 0.95, 2.72, 3.76, 5.00) [from measurements at E_d = 52 MeV]. See (1980AJ01) for references. For a summary of information on analog states of ¹²B and ¹²C see 12.12 (in PDF or PS) in (1980AJ01).

28. 14C(p, 3He)12B

Qm = -17.992

At E_p = 54 MeV, in addition to transitions to ¹²B*(0, 0.95, 5.61), the population of T = 2 states at E_x = 12.72 ± 0.07 and 14.82 ± 0.10 MeV is reported. The angular distribution of ³He ions to ¹²B*(12.75) is fittted by L = 0; that to ¹²B*(14.82) is rather featureless [its T = 2 character is assigned from the energies of the analog states]: both states have Γ_c.m. ≲ 200 keV (1976AS01). See also reaction 70 in ¹²C.