Be11: A shell model anomaly

Abstract

Abstract The Be 11 nucleus has been studied using the Be 9 (t,p) Be 11 reaction at 6 and 10 MeV triton energy. The Q value for the reaction was observed to be −1.164±0.015 MeV which corresponds to an energy difference between B 11 and Be 11 of 11.510±0.015 MeV. At 10 MeV triton energy 6 energy levels Be 11 were observed. These were at 0.319±10 MeV, 1.780± 0.025 MeV, 2.700±0.025 MeV, 3.410±0.025 MeV, 3.890±0.020 MeV and 3.960±0.020 MeV. The natural widths have also been measured for some of these states. Angular distributions of the protons from the reactions Be 9 (t,p) Be 11 and O 16 (t,p)O 18 were measured at 6 and 10 MeV in the first case and 10 MeV in the second case. The O 16 (t,p) O 18 angular distributions agreed well with double stripping theory and in contrast the Be 9 (t,p) Be 11 angular distributions were not interpretable. Angular distributions from the C 12 (t,α)B 11 reaction at 10 MeV triton energy were also studied in an attempt to obtain information on the spins and parities of some of the states in B 11 which are involved in the beta-decay of Be 11 . A comparison of the experimental results with the theoretical predictions on Be 11 by Talmi and Unna is included.