Channel-coupling effects in the resonating-group study of the seven-nucleon system

Abstract

A three-channel resonating-group calculation is performed to study the effects of channel coupling on the properties of the /sup 3/H+..cap alpha.. system. The channels included are /sup 3/H+..cap alpha.., n+ /sup 6/Li, and n+ /sup 6/Li( channels, with /sup 6/Li and /sup 6/Li( described by (1s)/sup 4/(1p)/sup 2/ harmonic-oscillator functions representing d+..cap alpha.. cluster configurations with relative orbital angular momenta equal to 0 and 2, respectively. By comparing with the /sup 3/H+..cap alpha.. single-channel result, it is found that the three-channel calculation improves the L = 1 ground state energy by 0.68 MeV and yields additional features such as cusps in the L = 0 and 2 phase shifts and a dispersionlike resonance structure in the L = 1 phase shift. In addition, it is noted that, in states with larger L values, the n+ /sup 6/Li( aligned configurations make particularly important contributions. Characteristics of nucleon-exchange terms have also been briefly investigated; here one finds that, as far as the /sup 3/H+..cap alpha.. system is concerned, the important one-exchange and core-exchange contributions are only weakly affected by the presence of other channels.