Anomalous results for the 9Be(α, t) 10B and 13C(α, t) 14N reactions at Eα = 27 meV

Abstract

Angular distributions for the reactions 9Be(α, t) 10B and 13C(α, t) 14N have been measured at E α = 27 MeV in the angular range 15°–110° c.m. for transitions to the first four states in 10B and the first five states in 14N. Excitation functions for 9Be(α, t) 10B measured at the lab angles 25° and 45° in the energy range 26–27.5 MeV showed little structure indicating a small compound nucleus contribution. For both reactions the transition to the 0 + T = 1 state is suppressed by at least a factor of five compared to the transition to the T = 0 states. DWBA and CCBA calculations gave a poor description of the data and did not predict the suppression of the T = 1 transitions in the (α, t) reactions. A reanalysis of more recent (d, n) and (τ, d) data in terms of the Cotanch-Robson isospin dependent DWBA model, which explains the spectroscopic factor ratio for T = 1 T = 0 transitions in the two reactions, is also presented.