Evaluation Home Page |
| Information on mass chains and nuclides |
|
 |
8B (1959AJ76)
(See the Energy Level Diagram for 8B)
GENERAL: See also Table 8.10 [Table of Energy Levels] (in PDF or PS).
Mass of 8B: The mass excess of 8B is 25.287 ± 0.008 MeV, from the threshold energy of the 6Li(3He, n)8B reaction.
| 1. 8B(β+)8Be | Qm = 17.978 |
| Q0 = 17.91 ± 0.12 MeV (1958VE20). |
The half-life of 8B is 0.78 ± 0.01 sec (1958DU78), 0.61 ± 0.11 sec (1952SH44), 0.65 ± 0.1 sec (1950AL57), 0.75 ± 0.02 sec (1958VE20). The decay proceeds mainly to the 2.9-MeV state of 8Be, log ft = 5.72 (1958VE20). See also (1958DU78) and 8Be.
| 2. 6Li(3He, n)8B | Qm = -1.976 |
The threshold has been observed, both in production of slow neutrons and of 8B positron activity, at E(3He) = 2.9661 ± 0.0017 MeV, yielding a mass excess of 25.287 ± 0.008 MeV. 8B is then stable with respect to 7Be + 1H by 138 ± 9 keV. Two additional thresholds † for slow neutron production are reported, in the range E(3He) = 2.9 to 6.0 MeV, at 3.9 ± 0.1 and 4.16 ± 0.05 MeV which may correspond to excited states of 8B at Ex = 0.6 ± 0.1 MeV (Γ = 0.2 ± 0.1 MeV) and 0.80 ± 0.05 MeV (Γ = 0.07 ± 0.04 MeV). It is pointed out that the existence of two low-lying levels in 8B would be rather surprising in view of the level structure of 8Li (1958DU78).
† Note added in proof: See, however, (1959FA02).
| 3. (a) 9Be(p, 2n)8B | Qm = -20.418 |
| (b) 10B(p, t)8B | Qm = -18.528 |
| (c) 12C(p, nα)8B | Qm = -26.136 |
See (1950AL57).
| 4. (a) 10B(γ, 2n)8B | Qm = -27.002 |
| (b) 11B(γ, 3n)8B | Qm = -38.456 |
| (c) 12C(γ, p3n)8B | Qm = -54.423 |
See (1952SH44).