Role of the Mechanism of Heavy Cluster Stripping in a 27Al(р, α)24Mg Reaction

Abstract

The contribution from the mechanism of heavy 23Na cluster stripping from a 27Al(5/2+) initial nucleus to a cross section of the 27Al(р, α)24Mg(0+, 2+) reaction is calculated at Ep = 7.4 MeV and angles of α‑particle emission of 25°–160° (laboratory). Calculations are made with the FRESCO code using the contribution from the 3/2+ ground state of 23Na. Spectroscopic amplitudes at decay vertices of 27Al(5/2+) → 23Na(3/2+) + α and 24Mg(0+, 2+) → 23Na(3/2+) + р reactions are determined from wave functions in the context of the Nilsson model, depending on their deformation. Cross sections calculated for the 0+ and 2+ levels of the 24Mg nucleus are two orders of magnitude lower than those found experimentally. The cross section for the 0+ level grows at θα ∼ 180° in the back semi-sphere, while the one for the 2+ level exhibits a maximum at θα > 140°. The slight contribution from the mechanism of heavy cluster stripping is due to the spectroscopic amplitudes at the decay vertices of the initial and final nuclei owing to a weak overlap of wave functions of 27Al, 23Na, and 24Mg(0+, 2+) nuclei in the Nilsson model.