1958AL96: ¹¹Be; measured T_1/2.

1958NU40: ¹¹Be; measured T_1/2.

1959WI49: ¹¹Be; measured T_1/2.

1970AL21: ¹¹Be; measured T_1/2.

1971AL07: ¹¹Be; measured T_1/2, E_γ, I_γ, delayed α-spectra, αγ-coin; deduced log ft. ¹¹B deduced levels, γ-branching.

1971ALZT: ¹¹Be; measured E_γ, I_γ, E_α, I_α; deduced log ft. ¹¹B deduced levels, J, π.

1980DEZF: ¹¹Li; measured E_β, I_β, β-delayed (particle)(particle)-coin. ¹¹Be deduced new decay modes. ¹¹Be levels deduced β-branching.

1981AL03: ¹¹Be; measured β-delayed E_α, β-delayed E(⁷Li), αγ-, ⁷Liγ-coin; deduced log ft, β-branching. ¹¹B level deduced α-branching.

1982MI08: ¹¹Be; measured E_γ, I_γ, γγ-coin; deduced log ft. ¹¹B levels deduced β-, γ-branching, B(λ).

1982WA18: ¹¹Be(β^-); measured βγ-coin, Doppler shift; deduced βν-asymmetry, meson exchange effects.

2013BO06: ¹¹Be(β^-p); analyzed available data; calculated beta-delayed proton emission.

2014RI01: ¹¹Be(β^-p); decay products using AMS, E_γ, I_γ, I_p, deduced β-p branching ratio, Gamow-Teller resonance strength.

2014RIZZ: ¹¹Be(β^-p); measured γ spectra from products of halo nucleus decay; deduced no conclusion for β delayed proton decay.

2017RI03: ¹¹Be(β^-p); analized available data; deduced one- or two-neutron halo decays.

2019AY03: ¹¹Be(β^-p); measured decay products, E_β, I_β, E_p, I_p; deduced level energy, resonance parameters, J, π.

2019RE03: ¹¹Be(β^-), (β^-α); measured β-delayed E_α and I_α; deduced β^--delayed α branching ratio, Gamow-Teller matrix elements, B(GT), log ft, and resonant strength by R-matrix analysis of the β-delayed α spectrum. ⁷Li; deduced levels, J, π, large overlaps between the two states in ⁷Li and the ground state of ¹¹Be.

2020RI02: ¹¹Be(β^-p); measured ¹⁰Be production after ¹¹Be decay, deduced β-p branching ratio.

2020VO05: ¹¹Be(β^-p), (β^-α); analyzed available data; found the present data cannot be explained in a reasonable shell model approach.

Measured half-life for ¹¹Be(β^-)¹¹B

Recommended value (July, 2015):	13.77 ± 0.08 s
Summary Table of Uncertainty Analysis:	(PDF)
Measured values:	13.6 ± 0.6 s	(1971AL07)
	13.81 ± 0.08 s	(1970AL21)
	13.57 ± 0.15 s	(1958AL96, 1959WI49)
	14.1 ± 0.3 s	(1958NU40)
Other Reviews:	13.74 ± 0.08 s	(2015BI05)

Previous Measurements

 

Decay to 11B* a (keV)	Jπ b	Branching Ratio (%) c		log ft		Transition to 11B* (MeV)	Eγ (keV)		Iγ (%) c
0	3/2-	A	54.7 ± 2.0 d	A	6.826 ± 0.016 n
		B	57 ± 3	B	6.81 ± 0.02
		C	61	C	6.78
2124.693 ± 0.027 e	1/2-	A	31.4 ± 1.8	A	6.644 ± 0.025 n	0	A	2124.473 ± 0.027	A	100
		B	29 ± 3	B	6.68 ± 0.04		B	2124.8 ± 0.7	B	33 ± 3
		C	29	C	6.68		C	2120 ± 10	C	32
4444.89 ± 0.50	5/2-	A	0.054 ± 0.004	A	8.83 ± 0.04 f, n	0	A	4443.90 ± 0.50	A	100
		B	< 0.06	B	> 10.9 g		B		B
		C	≤ 0.2	C	≥ 8.2		C		C
5020.31 ± 0.30	3/2-	A	0.282 ± 0.020	A	7.93 ± 0.03 n	0	A	5018.98 ± 0.40	A	85.6 ± 0.6
		B	0.28 ± 0.11	B	7.94 ± 0.14		B	5019.3 ± 1.7	B	0.47 ± 0.09
		C	≤ 0.2	C	≥ 8.2		C		C
						2.12	A	2895.30 ± 0.40	A	14.4 ± 0.6
							B	2893.1 ± 0.8	B	0.093 ± 0.028
							C		C
6742.7 ± 1.8 h	7/2- i	B	< 0.08	C	≥ 6.9
6791.80 ± 0.30 j	1/2+	A	6.47 ± 0.45	A	5.93 ± 0.03 n	0	A	6789.81 ± 0.50	A	67.5 ± 1.1
		B	6.8 ± 0.8	B	5.91 ± 0.05		B	6790.5 ± 1.8	B	4.51 ± 0.69
		C	6.5	C	5.92		C	6792 ± 6	C	4.4
						2.12	A	4665.90 ± 0.40	A	28.5 ± 1.1
							B	4666.3 ± 1.8	B	2.00 ± 0.28
							C	4640 ± 20	C	2.1
						5.02	A	1771.31 ± 0.30	A	4.0 ± 0.3
							B	1772.2 ± 0.7	B	0.28 ± 0.06
							C		C
7285.51 ± 0.43	5/2+	A	< 0.03	A	> 8.0 n	0	A	7282.92	A	87.0 ± 2.0
		B	< 0.16	B			B		B
		C	≤ 1.5	C	≥ 6.4		C		C
7977.84 ± 0.42 k	3/2+	A	4.00 ± 0.30	A	5.57 ± 0.04 n	0	A	7974.73	A	46.2 ± 1.1
		B	3.9 ± 0.5	B	5.58 ± 0.05		B	7974.7 ± 1.9	B	1.74 ± 0.30
		C	4.1	C	5.55		C	7970 ± 30	C	1.7
						2.12	A	5851.47 ± 0.42	A	53.2 ± 1.2
							B	5851.8 ± 1.8	B	2.13 ± 0.34
							C	5860 ± 40	C	2.4
						7.29	A	692.31 ± 0.10	A	0.85 ± 0.04
							B		B
							C		C
8559 i	≤ 5/2- i	B	< 0.06	B	> 7.0
		C	≤ 0.3	C	≥ 6.3
8920 i	5/2- i	B	< 0.02	B	> 8.5 g
		C	≤ 0.15	C	≥ 6.3
9876	3/2+	A	3.1 ± 0.4 l	A	4.23 ± 0.06 n
		B	3.0 ± 0.7 m	B	4.03 ± 0.15 m

A: (1982MI08).

B: (1971AL07).

C: (1958AL96, 1959WI49, 1964AL22).

a) Based on the γ-ray energies in Table I in (1982MI08).

b) From Table 11.4 in (1985AJ01).

c) Values in reference A are adopted from (1982MI08); based on their work and on the earlier work. Intensity in % per β-decay in reference B is normalized to (33 ± 3)% for the 2.13 MeV γ-intensity. Iγ (%) values in reference C is relative to all β-transitions.

d) From the relative intensities of the γ-rays and I2.13/Itotal β = 0.355 ± 0.018.

e) See also (1980WA25, 1981AL03).

f) log f1t ≈ 10.93.

g) log f1t. Q0 assumed to be 11.506 ± 0.007 MeV.

h) Energy derived from Ex of 11B*(6.79) and known ΔE of 4th and 5th excited states (1970BR23) [49.9 keV].

i) From Table 11.3 in (1980AJ01).

j) Transition to 11B*(4.44) is < 0.04%.

k) Transitions to 11B*(4.44, 5.02, 6.79) are < 0.06, < 0.09 and < 0.10%

l) From the relative intensities of the γ-rays and Iα/I2.13 of (1981AL03).

m) Value assumes 11B*(9.88) decays 100% to 7Lig.s.. See background information in (1971AL07). However, (1981AL03) determined 11B*(9.88) decays 87.4 ± 1.2 % to 7Lig.s. and 12.6 ± 1.2 % to 7Li*(0.48).

n) Using T1/2 = 13.76 ± 0.07 sec.

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¹¹C(β⁺)¹¹B Evaluated Data

A = 11 Beta-Decays Diagram

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Last modified: 06 October 2020