A continuum calculation of the neutron polarisation in the 3H+p reaction and the resonant states of 4He

Abstract

The energy dependence of the neutron polarisation P n in the 3H(p, n) 3He reaction is calculated using the 1p−1h coupled-channel model of nuclear reactions proposed earlier by Ramavataram et al. to describe the formation and decay of the negative parity excited states of A = 4. It is shown that the polarisation data provides tangible evidence for the T = 0, 1 − resonance predicted by them. Two positive parity T = 0 resonances proposed experimentally are also confirmed in this calculation. Inclusion of a 1 +, T = 0 resonance around 25 MeV and a 2 +, T = 0 resonance around 29 MeV is necessary to obtain agreement with experiment. It is shown that among these resonances the 1 +, T = 0 resonance can be generated at about the right energy in the coupled-channel calculation but that the 2 +, T = 0 resonance is too high in energy and it may be necessary to include 2p−2h configurations in this case. The proposed level scheme also provides a consistent description of the angular dependence of the differential cross section and polarisation P p in the elastic channel as well as the P n angular distribution.