Quasi-free (p, pα) scattering on 24Mg, 28Si, 40Ca and 58Ni at 157 MeV

Sixfold energy spectra have been measured for the (p, pα) reaction at 157 MeV on 24Mg, 28Si, 40Ca and 58Ni around quasi-free kinematic conditions. For the three s-d shell nuclei the experiment covered a map ranging from 0 to 220 MeV/c in recoil momentum and from 0 to 20 MeV in excitation energy of the final nucleus. Recoil momentum distributions have been obtained for the 0+ ground state and the 2+ first excited state of 20Ne, 24Mg and 36Ar, and also for the states around 4.4 MeV (mainly 4+) of 36Ar. The a spectroscopic factors extracted by a DWIA analysis are about three times larger than those predicted by the SU(3) model; however, they agree quite well in relative magnitude for a number of cases. The disagreement in shape between experiment and theory observed at low recoil momentum for the 2+ states might result from another reaction mechanism. The cross sections for 58Ni are about a factor often smaller than those for 40Ca. The 58Ni(p, pα)54Fe reaction seems to lead mainly to excited states of the final nucleus.