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GENERAL: See also (84AJ01) and Table 8.1 [Table of Energy Levels] (in PDF or PS).

Model calculations: (84VA06, 85PO10, 87BL18).

Complex reactions involving ⁸He: (82AL1C, 83AN13, 85MA13, 85TA1D, 86SA30, 87AR1G, 87BO40, 87KO1Z, 87PE1C, 87TA1F, 88GA10, 88ST06, 88TA1A).

Hypernuclei: (82KA1D, 83DO1B, 84BO1H, 85AH1A, 85IK1A, 86BA1W, 86DA1B, 87MI1A, 87PO1H).

Other topics: (83GL1B, 85AN28, 87AJ1A, 88AJ1B).

Ground-state properties of ⁸He: (83AN1C, 84FR13, 85SA32, 86HE26, 87BL18, 87HA30, 87SA15, 88JO1C).

Mass of ⁸He: The atomic mass excess of ⁸He adopted by us and by (88WA18) is 31598 ± 7 keV. ⁸He is then stable with respect to decay into ⁶He + 2 n by 2.137 MeV. See (79AJ01, 84AJ01).

The interaction nuclear radius of ⁸He is 2.48 ± 0.03 fm (85TA18, 85TA13) [see also for derived nuclear matter, charge and neutron matter r.m.s. radii].

1. 8He(β-)8Li

Qm = 10.652

The half-life of ⁸He is 119.0 ± 1.5 msec. The decay takes place (84 ± 1)% to ⁸Li*(0.98) [log ft = 4.20] and (16 ± 1)% via the neutron unstable states ⁸Li*(3.21, 5.4). (32 ± 3)% of the emitted neutrons then populate ⁷Li*(0.48). The decay to ⁸Li*(3.21, 5.4) suggest π = + for ⁸Li*(3.21) and 0⁺ or 1⁺ for ⁸Li*(5.4) (81BJ03). [(86BO41) suggest log ft = 5.0 for the transition to ⁸Li*(3.21)]. (86BO41) report β-delayed tritons with a branching ratio of (0.9 ± 0.1)%. This decay appears to require a 1⁺ state in ⁸Li at 8.8 MeV with a width, Γ_c.m. ~ 1 MeV; log ft is then 4.3 (86BO41). See also (88JO1C).

2. 9Be(7Li, 8B)8He

Qm = -28.264

At E(⁷Li) = 83 MeV, θ = 10°, the population of ⁸He_g.s., an excited state at 2.8 ± 0.4 MeV (presumably J^π = 2⁺) and a structure near E_x ~ 7 MeV are reported by (85AL1G). See also (85AL1B, 85AL29).

3. (a) 9Be(9Be, 10C)8He	Qm = -24.602
(b) 11Be(7Li, 10C)8He	Qm = -23.722

At E(⁹Be) = 106.7 MeV and at E(¹¹B) = 87 MeV the ground state of ⁸He is populated. In reaction (a) there is some evidence of a group corresponding to E_x = 2.6 ± 0.3 MeV, Γ = 1.0 ± 0.5 MeV, while in reaction (b) excited states are reported at E_x = 1.3, 2.6 and 4.0 MeV (± 0.3 MeV). The width of the latter is 0.5 ± 0.3 MeV (87BEYI). See also (88BEYJ).