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11Be (1990AJ01)(See Energy Level Diagrams for 11Be) GENERAL: See also (1985AJ01) and Table 11.2 [Table of Energy Levels] (in PDF or PS). Model calculations:(1984MI1H, 1984VA06, 1986WI04). Electromagnetic transitions:(1984MI1H, 1984VA06, 1987HO1L). Complex reactions involving 11Be:(1985BO1A, 1986AV1B, 1987TR05, 1987WA09, 1988BA53, 1988RU01, 1988TA1N, 1988TR03, 1989SA10). Muon and neutrino capture and reactions:(1984KO24). Hypernuclei:(1985IK1A, 1986ME1F). Other topics:(1984MI1H, 1985AN28, 1986AN07). Ground-state properties of 11Be:(1984FR13, 1987SA15, 1987VA26, 1989BE03). The interaction matter radius of 11Be is 2.86 ± 0.04 fm (1988TA10). See also (1989SA10, 1989TA1K).
The decay is complex: see reaction 26 in 11B and Table 11.12 (in PDF or PS). The half-life is 13.81 ± 0.08 s (1970AL21). See also (1980AJ01).
Proton groups have been observed to the states displayed in Table 11.2 (in PDF or PS). τm for the first excited state is 166 ± 15 fs, corresponding to a very large E1 transition strength of 0.36 ± 0.03 W.u.; Eγ = 320.04 ± 0.10 keV. The Jπ of 11Be*(0.32) is 1/2-, as determined by a study of the yield of 320 keV γ-rays as a function of time in μ- capture by 11B. The strength of the E1 transition fixes Jπ of 11Beg.s. to be 1/2+ or 3/2+, using the parity information obtained from the nature of the β- decay of the ground state [see reaction 26 in 11B]. 11Be*(5.24, 6.71, 8.82) are strongly populated at Et = 20 MeV indicating that these states have a large overlap with 9Beg.s. + 2n. See (1980AJ01, 1985AJ01) for references.
Angular distributions of the p0 and p1 groups have been measured at Em = 6 MeV and 12 MeV: ln = 0 [and therefore Jπ = 1/2+ for 11Be(0)] and l, S = 0.73 ± 0.06 and 0.63 ± 0.15, respectively. At Em = 25 MeV 11Be*(0, 0.32, 1.78) are strongly populated: S = 0.77, 0.96, and 0.50, respectively, Jπ = (5/2, 3/2)+ for 11Be*(1.78) [ln = 2]. See (1980AJ01) for references.
See 11Li.
The photon spectrum from stopped pions includes a peak corresponding to 11Be*(0 + 0.32) (1986PE05).
See (1987BL07; Eπ- = 145 MeV).
At E(7Li) = 82 MeV 11Be*(0 + 0.32, 1.8, 3.4) are populated (1985AL1G).
At E(6Li) = 80 MeV, 11Be*(0.32) is strongly populated and the angular distribution to this state has been measured. 11Be*(2.69, 4.0) are also observed: see (1980AJ01).
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