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USNDP

7He (88AJ01)


(See the Isobar Diagram for 7He)

GENERAL: See also (84AJ01) and Table 7.1 [Table of Energy Levels] (in PDF or PS).

Hypernuclei: (82KA1D, 83FE07, 84AS1D, 85KO1G, 85DA1B, 86DO01, 86ME1F).

Other topics: (83ANZQ, 84FR13, 84VA06, 86GI10, 86SH1L, 87BO40, 87GOZN, 87PE1C).

Mass of 7He: The atomic mass excess of 7He is 26.11 ± 0.03 MeV: 7He is then unbound with respect to decay into 6He + n by 0.44 MeV: see (84AJ01). The ground state is calculated to have Jπ = 3/2- and to be unstable with respect to decay into 6He + n by about 1 MeV (85PO10). [I am indebted to F.C. Barker for his comments.] See also (87BEYI).

1. 7Li(π-, γ)7He Qm = 128.37

Capture γ-rays from the transition to 7Heg.s. are reported by (86PE05).

2. 7Li(n, p)7He Qm = -10.42

The proton group corresponding to 7Heg.s. has Γ < 0.2 MeV: see (79AJ01). At En = 60 MeV broad bumps in the spectra are ascribed to states at Ex ~ 20 ± 1 MeV [Γ = 9 ± 2 MeV] and, possibly, at ~ 6 MeV (84BR03, 83BR1C) [see for discussion of the GDR]. See also (87HE24) and (87BR32).

3. 7Li(t, 3He)7He Qm = -11.18

The 3He particles to the ground state of 7He have been observed at Et = 22 MeV. The width of the ground state is 160 ± 30 keV; for a radius of 2.2 fm and ln = 1, this width is 0.22 of the Wigner limit. The angular distribution is peaked in the forward direction. No other states of 7He were observed for Ex < 2.4 MeV: see (79AJ01).

4. (a) 7Li(7Li, 7Be)7He Qm = -12.07
(b) 7Li(11B, 11C)7He Qm = -13.19
(c) 9Be(6Li, 8B)7He Qm = -23.60
(d) 9Be(9Be, 11C)7He Qm = -14.07
(e) 9Be(11B, 13N)7He Qm = -11.44
(f) 9Be(14C, 16O)7He Qm = -7.01

At E(6Li) = 72 MeV and at E(7Li) = 70 MeV (reactions (a) and (c)) there is no evidence for excited states with Γ < / = 2 MeV for Ex < 10 MeV (85AL1G, 85AL1B, 85AL29). The ground state of 7He is strongly populated. Reactions (b), (d), (e) and (f) have been investigated at E(11B) = 88, E(9Be) = 106.7 and E(14C) = 152.6 MeV. The ground state of 7He is populated. There is some evidence for a second state in reaction (f) at Ex = 2.9 ± 0.5, Γ = 1.5 ± 0.5 MeV (87BEYI). See also (79AJ01) and (88BEYJ).