Study of the p + ^3H and n + ^3He Final-State Interactions in the Reactions ^7Li(p,ɑ) and D(^3He,p)

Abstract

The ɑ-particle energy spectra from the bombardment of 7Li with 9.1-MeV protons have been obtained at 2.5° ≤ ϴɑ ≤ 120°. The high-energy ends of the spectra are interpreted as due to the 1S p + 3H final-state interaction through the first excited state of 4He at 20.06 MeV. The factored-wave-function method is used to deduce the resonance parameters of this state. Consistency in the use of this method is obtained by a PWBA calculation based on the triton-transfer mechanism to account for the forward-peaking in the angular distribution. Coincidence measurements between a-particles and the other charged particles give additional evidence for the 0+ assignment to the state, and indicate that the a + 3H and a + H final-state interactions are important as the 4He excitation energy gets higher. To reduce the effects of these final-state interactions, the reaction D(3He, p), at a 3He bombarding energy of 16.5 MeV, has been investigated. The protons emitted from the reaction have been measured at ϴp = 30° in coincidence with the other charged particles. Angular correlations have been obtained for 6.6 MeV ≤ Ep ≤ 8.6 MeV, and compared with a modified Born approximation calculation based on the stripping of 3He. The angle-energy correlation and the p - 3H to p - 3He branching ratio can be reproduced, if Meyerhof's p + 3H phase shifts and Bransden's n + 3He phase shifts are used to describe their respective interactions in the final states. In agreement with the reported 0- state at 21.2 MeV, the p-wave final-state interactions are found to be important in this energy range.