(See Energy Level Diagrams for 11Be)
Proton groups have been observed to the states displayed in Table 11.3 (in PDF or PS). τm 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.; Eγ = 320.04 ± 0.10 keV (see (1983MI08)). 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 28 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. + two neutrons. See (1980AJ01) for references.
Angular distributions of the p0 and p1 groups have been measured at Ed = 6 MeV and 12 MeV: ln = 0 [and therefore Jπ = 1/2+ for 11Be(0)] and 1, S = 0.73 ± 0.06 and 0.63 ± 0.15, respectively. At Ed = 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.
† Certain reactions on which no new work has been published will not be discussed in this review: see (1980AJ01).
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).