A study of the reactions Be 9(He 3,n)C 11, Li 7(He 3,n)B 9 and C 13(He 3,n)O 15

Abstract

Time-of-flight techniques with time resolution capabilities of 4 ns for neutrons have been used to study (He 3,n) reactions with the following targets: Be 9, Li 7 and C 13. The angular distributions of neutrons to the ground state and the first four excited states (2.00, 4.32, 4.81 and the unresolved doublet at 6.35 and 6.49 MeV) of C 11 have been measured for the reaction Be 9 (He 3,n)C 11 at an incident He 3 energy of 2.1 MeV. Excitation functions were measured for these states for E He 3 from 1.2 to 2.7 MeV at laboratory angles of 0° and 81.5°. For the Li 7 (He 3,n)B 9 reaction an angular distribution was measured at E He 3=2.1 MeV for the ground state neutron group from B 9 and the yield curve was measured for this group from 1.2 to 2.7 MeV at 0°. For the C 13(He 3,n)O 15 reaction resolved neutron groups were seen for transitions to the ground and third excited states (6.15 MeV) in O 15. Excitation functions were measured at laboratory angles of 0° and 90° for this reaction for E He 3 from 1.2 to 2.7 MeV and angular distributions were measured at E He 3=2.66 MeV. Distorted wave calculations have been made in an attempt to describe all of the reactions. In general, the calculations can be made to fit the angular distributions quite well in the forward direction but the back angle cross sections predicted by the calculations are usually much lower than the measured values. Tentative spin and parity assignments are given for the resolved groups.