12B

β--Decay Evaluated Data



Measurements
1948JE03: 12B; measured T1/2.
1956TA07, 1957CO59, 1958CO66, 1958KA31: 12B.
1957CO57: 12B; measured T1/2.
1958KR65: 12B; measured T1/2.
1959FA03: 12B; measured T1/2.
1961SC09: 12B; measured not abstracted; deduced nuclear properties.
1962NE14: 12B; measured not abstracted; deduced nuclear properties.
1962PO02: 12B; measured not abstracted; deduced nuclear properties.
1963AL15: 12B; measured not abstracted; deduced nuclear properties.
1963FI05: 12B; measured not abstracted; deduced nuclear properties.
1963PE10: 12B; measured not abstracted; deduced nuclear properties.
1963WI05: 12B; measured not abstracted; deduced nuclear properties.
1972AL31: 12B(β-); measured βγ-coin; deduced log ft, β-branching.
1974MC11: 12B; measured Eβ, Iβ, βγ-coin; deduced log ft.
1978AL01: 12B(β-); measured Eβ, Iβ, βγ-coin, T1/2; deduced β-branching, mirror asymmetries, ft.
1981KA31: 12B(β-); measured βγ-coin, βγ(t); deduced Iβ, log ft.
1983HAZE: 12B(β-); measured β asymmetry.
1985MAZL: 12B(β-); measured Iβ(θ); deduced alignment correlation coefficients.
1986CU01: 12B(β-); measured β-decay T1/2.
1986RO27: 12B(β-); measured T1/2.
1987MI20: 12B(β-); measured Iβ(θ), aligned nuclei; deduced weak nucleon current parity conservation in isospin space.
1988NA09: 12B; measured I(β), I(γ), βγ-coin; deduced mirror asymmetry. Deduced Gamow-Teller β-decay branching ratio.
1988SA04: 12B(β-); measured β-decay T1/2.
1988SHZO: 12B(β-); measured Eβ; deduced shape factor.
1990CA10: 12B(β-); measured spectral shape factors.
1991SOZW: 12B(β-); measured NMR, β asymmetry. 12B deduced quadrupole moment.
1992BA11: 12B; calculated Gamow-Teller β-decay ft-value asymmetry. R-matrix approach.
1992OHZW: 12B(β-); measured NMR. 12B deduced Q.
1992SHZI: 12B(β-); measured Eβ.
1992SOZS: 12B(β-); measured β(E, θ); deduced polarization correlation coefficient.
1992TAZP: 12B(β-); measured T1/2. 12C deduced levels, ft-value asymmetries.
1993MI32: 12B(β-); measured Iβ(θ); deduced alignment coefficients, Gamow-Teller matrix elements axial vector time component ratio.
1993MI36: 12B(β-); measured modified β-NMR spectra in Mg; deduced quadrupole moment.
1993OH05: 12B(β-); measured modified β-NMR spectra; deduced hyperfine interactions, quadrupole moment.
1994MO23: 12B(β-); analyzed Iβ(θ) data, aligned nuclei; deduced induced tensor current limit, axial charge.
1994OH03: 12B(β-); measured β-NMR. 12B level deduced quadrupole moment.
1995KO28: 12B(β-); analyzed Iβ(θ); deduced ft value, y asymmetry characteristics, induced tensor coupling constant.
1995OK04: 12B(β-); measured β NMR; deduced μ.
1996IZ02: 12B(β-); measured β-NMR; deduced electric quadrupole moments.
1997CO15: 12B(β-); measured β-asymmetry; deduced alignment related features.
1997MA21: 12B(β-); measured Eβ, β(θ). 12B deduced μ.
1997MIZS: 12B(β-); measured alignment correlation terms in β-ray angular distribution from aligned 12B; deduced validity of G-parity conservation law.
1997NE01: 12B(β-); measured β-asymmetry; deduced 12B alignment related features. Level mixing resonance method.
1997OZZY: 12B(β-); measured β(t), T1/2.
1997YAZW: 12B(β-); measured alignment correlation terms in β-ray angular distribution from aligned 12B; deduced large enhancement in the axial charge.
1998MA27: 12B(β-); measured β-NMR; deduced alignment correlation terms.
1998MI14: 12B(β-); measured β-ray angular distribution from oriented nuclei; deduced nonzero G-parity violating induced tensor form factor.
1998MIZU: 12B(β-); measured Iβ(θ) from spin aligned nuclei; deduced alignment correlation coefficients, second class weak nucleon current.
1998OHZZ: 12B(β-); measured Eβ; deduced spectral shape factor.
1999CO09: 12B(β-); measured β asymmetry. 12B deduced μ, quadrupole moment.
1999MI41: 12B(β-); measured Eβ, Iβ(θ) from aligned nuclei; deduced G-parity violating induced tensor form factor.
2000MI11: 12B(β-); measured β angular distributions from aligned nuclei; deduced axial charge.
2000MIZQ: 12B(β-); measured β-NMR; deduced G-parity irregularity.
2000ST19: 12B(β-); measured Eβ, Iβ.
2002MI01: 12B(β-); measured Eβ, angular distributions from spin-aligned sources; deduced axial charge.
2002MI03, 2002MI49, 2002MIZZ: 12B(β-); measured Eβ, angular distributions from spin-aligned sources; deduced tensor form factor, constraints on Kubodera-Delorme-Rho parameters.
2002MI36: 12B(β-); measured Eβ, Iβ(θ, H, t) from oriented nuclei; deduced alignment correlation terms, axial charge.
2003MI24: 12B(β-); measured Eβ, angular distributions from spin-aligned sources; deduced G-parity irregular induced tensor coefficient.
2003ZH32: 12B(β-); measured β-NMR, T1/2; deduced μ.
2004FY02: 12B(β-); analyzed β-delayed Eα, αα-coin. 12C deduced resonance features.
2005DI16: 12B(β-); measured β-delayed Eα, αα-coin. 12C deduced excited states, J, π. R-matrix analysis.
2007MI49: 12B(β-); measured β-assymetry for spin polarized nuclei implanted in Pt foil using the β-NMR method.
2007PEZY: 12B(β-); measured branching β-decay ratios.
2009DI06: 12B(β-); measured Eα, Eγ, ααα-coin. 12C; deduced levels, J, π, triple-α continuum states and their decay modes.
2009HY01: 12B(β-); deduced branching ratio, log ft, B(GT) to various 12C states.
2009HY02: 12B(β-); measured Eα, Iα, Eγ, Iγ, Eβ, βγ-, βα-, ααα-coin. 12C; deduced levels, β feedings, and log ft. Triple-α method and R-matrix analysis.
2010HY01: 12B(β-); measured 3α summed spectra and associated branching ratios for breakup via the 8Be ground-state and via excited states of 8Be. 12C; deduced levels, resonances, Gammow-Teller strengths and widths using multilevel, many-channel R-matrix formalism.
2014TE01: 12B(β-); measured decay products, Eβ, Iβ; deduced breakup of excited states in 12C.
2016MU06: 12B(β-); measured Eγ, Iγ, γγ-coin, γγ(θ) for the Hoyle state. 12C; deduced first excited 2+ and 0+ levels, β branching ratio to the Hoyle state in 12C, log ft.

Measured half-life for 12B(β-)12C

Recommended value (September, 2015): 20.22 ± 0.04 ms: Weighted average with external uncertainty
Summary Table of Uncertainty Analysis:   Table 12B preview (PDF)  
Measured values: 20.18 ± 0.72 ms (2003ZH32)
20.20 ± 0.02 ms (1978AL01)
20.3 ± 0.1 ms (1963FI05)
20.2 ± 0.2 ms (1963PE10)
20.80 ± 0.15 ms (1962NE14)
20.15 ± 0.2 ms   (1962PO02)
20.31 ± 0.20 ms (1961SC09)
20.4 ± 0.4 ms (1959FA03)
18.87 ± 0.50 ms (1959KR1B)
20.7 ± 0.3 ms (1958BU1E)
20.6 ± 0.2 ms (1958KR65)
18+1.5-1.3 (1957CO57)
22 ± 1 ms (1953BR1B)
27 ± 2 ms (1948JE03)
22 ± 2 ms (1939BE1A)

Previous Measurements

Decay to 12C*
(MeV ± keV) c
Jπ Branching Ratio (%) Log ft
0 b 0+   (1958CO66) 97 (1958CO66) 4.1 ± 0.1 a
(1974MC11) 97.13 ± 0.31     (1974MC11) 4.072 ± 0.002  
(1978AL01) 97.14 ± 0.30     (1978AL01) 4.067 ± 0.002 f
(1968AJ02) 97.1   4.075 ± 0.002 g
(1990AJ01) 97.22 ± 0.30       4.066 ± 0.002 k
Adopted 98.300 ± 0.028 h  Adopted 4.0618 ± 0.0009 i 
4.43982 ± 0.21    2+   (1956TA07) 1.7 ± 0.4   (1958CO66) 5.1 ± 0.2 a
(1958KA31) 1.4 ± 0.4      
(1963PE10) 1.3 ± 0.1     5.10 ± 0.03 g
(1972AL31) 1.27 ± 0.06   (1974MC11) 5.11 ± 0.02  
(1978AL01) 1.276 ± 0.05     (1990AJ01)  5.108 ± 0.014 k
Adopted / (1981KA31) 1.182 ± 0.019   Adopted / (1981KA31) 5.143 ± 0.007 i
7.65407 ± 0.19 d 0+   (1957CO59, 1958CO66) 1.3 ± 0.4   (1958CO66)  4.2 ± 0.3 a
(1963AL15) 1.1 ± 0.3 j    4.14 ± 0.10 g
(2009HY01)      0.54 ± 0.02 m, n (1990AJ01)  4.13 ± 0.09 k
(2016MU06)  0.63 ± 0.11 o    
Adopted 0.54 ± 0.02   Adopted 4.574 ± 0.017 i 
     10.3 ± 300 e (0+) l (1958CO66) 0.13 ± 0.04 p (1958CO66) 4.1 ± 0.4 a
(1963WI05) 0.07 ± 0.02 p 4.2 ± 0.2 g
Adopted 0.062 ± 0.003   Adopted 4.29 ± 0.20 i 
[9 - 12 MeV] r   (2009HY01)      0.063 ± 0.003 m, n    
     0.055 ± 0.007 q, n    
12.7 1+ (2009HY01) (2.6 ± 0.2) × 10-4 m, n    
(3.2 ± 0.7) × 10-4 q, n    
Adopted (2.6 ± 0.2) × 10-4       Adopted 3.91 ± 0.04 i 
a) Based on T1/2 = 20.6 ms.
b) Eβ- = 13.381 ± 0.041 MeV (1962MA22).
c) See (2017KE05).
d) See (1976NO02).
e) Γ = 3.0 ± 0.7 MeV, θ2α = 1.5 (1966SC23).
f) Based on Qm and T1/2 = 20.20 ms (1985AJ01).
g) Based on Qm and T1/2 = 20.41 ms: see (1966BA1A).
h) 100% minus the branching ratios measured to excited states.
i) Based on Qm = 13369.4 ± 1.3 keV and T1/2 = 20.20 ± 0.02 ms.
j) In the original manuscript, the value (1.7 ± 0.5)% is calculated using Γγ/Γ = (2.9 ± 0.3) × 10-4 and B(4.4) = (1.3 ± 0.1)%. Here we used Γγ/Γ = 4.16 and B(4.4) = (1.182 ± 0.019)%.
k) Based on Qm and T1/2 = 20.20 ± 0.02 ms (M.J. Martin, private communication to Fay Ajzenberg-Selove (1990AJ01).
l) (1958CO66) suggest J = 0+.
m) Analysis of KVI data in (2009HY01).
n) In (2009HY01) the branching ratios are normalized to B(4.44) = (1.28 ± 0.04)% from (1990AJ01). In the present evaluation we adopted (1.182 ± 0.019)%. In the table the (2009HY01) values have been renormalized (decreased) to the updated B(4.44).
o) In the original manuscript, the value (0.64 ± 0.11)% is calculated using Γγ/Γ = (4.07 ± 0.11) × 10-4. Here we used Γγ/Γ = (4.16 ± 0.11) × 10-4.
p) The analysis neglected β feeding to C*(12.71).
q) Analysis of JYFL data in (2009HY01).
r) (2009HY01) integrated the strength in the Ex = 9 - 12 MeV region rather than attributing the strength to a 10.3 MeV group, see discussion.

12Be(β-)12B Evaluated Data

12N(β+)12C Evaluated Data

A = 12 Beta-Decays Diagram

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Last modified: 21 May 2018