Excitation Functions and Angular Distributions of the Reactions Al²⁷(<i>p</i>, α)Mg²⁴ at 12.7∼14.1 Mev and Cr⁵²(<i>p</i>, α)V⁴⁹ at 9.0∼14.2 Mev

Abstract

Making use of a proportional counter, alpha particles have been observed from the reactions Al 27 ( p , α)Mg 24 resulting in the ground and first excited states of Mg 24 and Cr 52 ( p , α)V 49 resulting in the lowest three and a few higher states. Excitation curves have been measured at a laboratory angle of 50° with respect to the bombarding beam, from 12.7 to 14.1 Mev for Al 27 ( p , α)Mg 24 and from 9.0 to 14.8 Mev for Cr 52 ( p , α)V 49 . The former shows a sharp energy dependence, while the latter shows a fairly smooth structure. Angular distributions have been measured at 14.1, 13.0 and 12.8 Mev for Al 27 ( p , α)Mg 24 and at 14.2, 13.0, 12.0, 11.0, 10.0, 9.5 and 9.0 Mev for Cr 52 ( p , α)V 49 . Although the Al 27 ( p , α 0 )Mg 24 data can be partially fitted by [ j 2 ( Q γ 0 ] 2 of Butler's theory, some angular distributions show strong backward peaking. Either interference between various direct interaction processes or between direct interaction and compound nuclear processes, or both are responsible for this reaction. The approximate 90° symmetry of Cr 52 ( p , α)V 49 angular distribution does not appear to be inconsistent with the statistical theory of nuclear reactions. However, the conspicuous forward peak at higher energies, especially at 14.2 Mev, is considered to indicate the increasing contribution of direct interaction processes.