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GENERAL: See also (74AJ01).

See (AL73L, TO73G, IR74A, MA74S, AB75A, BE75Q, BE76L, IR76C, VA76L, KO78F, NA78E).

Mass of ⁸He: The atomic mass excess of ⁸He is 31596 ± 7 keV (TR77). See also (CE74D, JA75E, KO75F, RO78A). ⁸He is then stable with respect to decay into ⁶He + 2n by 2.141 MeV. See also (74AJ01, TR76) and (JE75; theor.). The IMME coefficients based on the latest masses of the T = 2 states in A = 8 are calculated by (TR77).

1. 8He(β-)8Li

Qm = 10.649

The half-life is 122 ± 2 msec. The decay takes place 88% to ⁸Li*(0.98) [log ft = 4.19 (M.J. Martin, Nucl. Data Project, private communication.)] [consistent with J^π = 1⁺ for ⁸Li*(0.98)] and (12 ± 1)% via ⁸Li states which decay by neutron emission (PO65H). See also (AN73L, DE76N).

2. 18O(α, 14O)8He

Qm = -37.962

At E_α = 58 MeV, θ_lab = 8°, the differential cross for formation of ⁸He_g.s. is 40 ± 15 nb/sr (JA75E).

3. 26Mg(α, 22Mg)8He

Qm = -44.989

This reaction has been studied at E_α = 80 MeV (CE66A) and 110.6 MeV (CE74D).