O18+C12andO18+C13fusion-evaporation reactions

Abstract

The evaporation residues of the ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ reactions have been identified by nuclear charge Z and atomic mass $A$ with an ionization chamber used in conjunction with time-of-flight measurements. A dominant decay mode can be assigned for each residual nucleus from the shape of the angular distributions. The predictions of two different evaporation calculations are in satisfactory agreement with the experimental results except for an anomalously large ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ experimental yield in both reactions which cannot be explained. The evaporation schemes of the two neighboring compound nuclei ${}_{}{}^{30}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^{31}{}_{}{}^{}\mathrm{Si}$, formed at nearly equal excitation energy and spin, are compared.