
^{11}Be (1990AJ01)(See Energy Level Diagrams for ^{11}Be) 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 ^{11}Be:(1985BO1A, 1986AV1B, 1987TR05, 1987WA09, 1988BA53, 1988RU01, 1988TA1N, 1988TR03, 1989SA10). Muon and neutrino capture and reactions:(1984KO24). Hypernuclei:(1985IK1A, 1986ME1F). Other topics:(1984MI1H, 1985AN28, 1986AN07). Groundstate properties of ^{11}Be:(1984FR13, 1987SA15, 1987VA26, 1989BE03). The interaction matter radius of ^{11}Be is 2.86 ± 0.04 fm (1988TA10). See also (1989SA10, 1989TA1K).
The decay is complex: see reaction 26 in ^{11}B and Table 11.12 (in PDF or PS). The halflife 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). τ_{m} for the first excited state is 166 ± 15 fs, corresponding to a very large E1 transition strength of 0.36 ± 0.03 W.u.; E_{γ} = 320.04 ± 0.10 keV. The J^{π} of ^{11}Be*(0.32) is 1/2^{}, as determined by a study of the yield of 320 keV γrays as a function of time in μ^{} capture by ^{11}B. The strength of the E1 transition fixes J^{π} of ^{11}Be_{g.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 ^{11}B]. ^{11}Be*(5.24, 6.71, 8.82) are strongly populated at E_{t} = 20 MeV indicating that these states have a large overlap with ^{9}Be_{g.s.} + 2n. See (1980AJ01, 1985AJ01) for references.
Angular distributions of the p_{0} and p_{1} groups have been measured at E_{m} = 6 MeV and 12 MeV: l_{n} = 0 [and therefore J^{π} = 1/2^{+} for ^{11}Be(0)] and l, S = 0.73 ± 0.06 and 0.63 ± 0.15, respectively. At E_{m} = 25 MeV ^{11}Be*(0, 0.32, 1.78) are strongly populated: S = 0.77, 0.96, and 0.50, respectively, J^{π} = (5/2, 3/2)^{+} for ^{11}Be*(1.78) [l_{n} = 2]. See (1980AJ01) for references.
See ^{11}Li.
The photon spectrum from stopped pions includes a peak corresponding to ^{11}Be*(0 + 0.32) (1986PE05).
See (1987BL07; E_{π} = 145 MeV).
At E(^{7}Li) = 82 MeV ^{11}Be*(0 + 0.32, 1.8, 3.4) are populated (1985AL1G).
At E(^{6}Li) = 80 MeV, ^{11}Be*(0.32) is strongly populated and the angular distribution to this state has been measured. ^{11}Be*(2.69, 4.0) are also observed: see (1980AJ01).
