
^{11}Be (1985AJ01)(See Energy Level Diagrams for ^{11}Be) GENERAL: See also (1980AJ01) and Table 11.3 [Table of Energy Levels] (in PDF or PS). Model calculations:(1981RA06, 1981SE06, 1983MI1E, 1984VA06). Electromagnetic transitions:(1980MI1G). Complex reactions involving ^{11}Be:(1979BO22, 1980WI1L, 1983EN04, 1983WI1A, 1984GR08, 1984HI1A). Hypernuclei:(1979BU1C, 1982IK1A, 1982KA1D, 1982KO11, 1983FE07, 1983KO1D, 1983MI1E). Other topics:(1981SE06, 1982NG01). Groundstate properties of ^{11}Be:(1981AV02, 1982NG01, 1983ANZQ).
The decay is complex: see reaction 28 in ^{11}B and Table 11.13 (in PDF or PS). The halflife is 13.81 ± 0.08 sec (1970AL21). See also (1980AJ01).
Proton groups have been observed to the states displayed in Table 11.3 (in PDF or PS). τ_{m} for the first excited state is 166 ± 15 fsec (1983MI08), corresponding to a very large E1 transition strength of 0.36 ± 0.03 W.u.; E_{γ} = 320.04 ± 0.10 keV (see (1983MI08)). 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 28 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.} + two neutrons. See (1980AJ01) for references.
See (1975AJ02).
Angular distributions of the p_{0} and p_{1} groups have been measured at E_{d} = 6 MeV and 12 MeV: l_{n} = 0 [and therefore J^{π} = 1/2^{+} for ^{11}Be(0)] and 1, S = 0.73 ± 0.06 and 0.63 ± 0.15, respectively. At E_{d} = 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.
^{†} Certain reactions on which no new work has been published will not be discussed in this review: see (1980AJ01). See ^{11}Li.
At E(^{7}Li) = 82  83 MeV groups corresponding to ^{11}Be*(0, 1.8, 3.4) are reported by (1982AL08, 1983AL20).
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).
