Macroscopic description of exchange effects in light-ion interactions withO16

Abstract

Exchange effects in the $\alpha$+${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ + ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, and $p$+${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ systems are examined by studying the behavior of phase shifts and cross sections calculated with the resonating-group method. The result shows that these effects can be approximately represented by an exchange potential $V_{\mathrm{ex}}=V_a+{\mathrm{}(-1\mathrm{})\mathrm{}}^l{V}_b$. The term $V_a$, representing mainly the knockout process, is found to have an appreciable magnitude and to have a range shorter than that of the direct nuclear potential. The term ${\mathrm{}(-1\mathrm{})\mathrm{}}^l{V}_b$, representing mainly the heavy-particle pickup process, is, on the other hand, rather small in all these three systems. Based on the findings obtained from this and previous investigations, an empirical rule is given which indicates the situation under which the heavy-particle pickup process is expected to be important.