11Be

β--Decay Evaluated Data



Measurements
1958AL96: 11Be; measured T1/2.
1958NU40: 11Be; measured T1/2.
1959WI49: 11Be; measured T1/2.
1970AL21: 11Be; measured T1/2.
1971AL07: 11Be; measured T1/2, Eγ, Iγ, delayed α-spectra, αγ-coin; deduced log ft. 11B deduced levels, γ-branching.
1971ALZT: 11Be; measured Eγ, Iγ, Eα, Iα; deduced log ft. 11B deduced levels, J, π.
1980DEZF: 11Li; measured Eβ, Iβ, β-delayed (particle)(particle)-coin. 11Be deduced new decay modes. 11Be levels deduced β-branching.
1981AL03: 11Be; measured β-delayed Eα, β-delayed E(7Li), αγ-, 7Liγ-coin; deduced log ft, β-branching. 11B level deduced α-branching.
1982MI08: 11Be; measured Eγ, Iγ, 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.

Measured half-life for 11Be(β-)11B

Recommended value (July, 2015): 13.77 ± 0.08 s
Summary Table of Uncertainty Analysis:        Table 11Be preview (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.

11Li(β-)11Be Evaluated Data

11C(β+)11B Evaluated Data

A = 11 Beta-Decays Diagram

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Last modified: 21 May 2018