(p, alpha) reactions on 1p, 2s-1d shell nuclei

The 12C(p, \u3b1)9B and 32S(p, \u3b1)29P reactions have been studied at incident energies of 42.77 and 41.9 MeV, respectively. The experimental (p, \u3b1) relative cross sections are well reproduced by distorted wave direct pickup calculations with a semimicroscopic form factor and current shell model wave functions. A comparison between (p, \u3b1) and (3He,d) spectra on 1p and 2s-1d shell nuclei, leading to the same final nucleus, shows a clear evidence of a dominant pickup process over the knockout mechanism in the dynamics of the (p, \u3b1) reaction