Low-energy M1 strength in the Li-7(p,gamma o)Be-8 reaction

The Li-7(p, gamma 0)Be-8 reaction is studied in a microscopic cluster model. All relevant subsystem properties are well reproduced. The calculated astrophysical S-factor is in good agreement with the experimental data, although some M1 strength is missing in the 1(+); 1 resonance region, and there is no contribution from the 1(+);0 stare. Our model predicts, in contradiction to experiment, a dominant I = 1 channel spin contribution to the cross section. We estimate an M1 strength of 3.5% at 80 keV. By assuming the experimental resonance parameters and channel spin ratio for the first 1(+) state that M1 strength is 6.3%, in good agreement with an R-matrix analysis,