Radiative Ml capture in light nuclei

The importance of semi-direct processes in E1 and E2 capture reactions has been well documented. Little is known, however, about M1 capture although a vast body of data indicates a non-statistical nature. We discuss here the importance of the semi-direct M1 process and concentrate in particular on recent experimental results claiming that the M 1 strength in²⁹Si isnearly one order of magnitude smaller than in ²⁸Si, the target nucleus. We use shell model arguments to demonstrate that this reduction is indeed consistent with the semi-direct reaction process and that other mechanisms like2p-2h fragmentation and phonon coupling are not likely to be instrumental in elucidating further the non-statistical nature of the²⁸Si+n reaction.