Systematics of carbon + carbon fusion-evaporation reactions

Abstract

Carbon + carbon fusion-evaporation reactions have been studied in two series of measurements: (i) The system ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ has been studied for laboratoryy bombarding energies betwen 30 and 60 MeV in 5-MeV steps. Angular distributions for all residual nuclei have been measured and the corresponding yields versus bombarding energy are compared to a fusion-evaporation calculation. It is also shown that, at least at one bombarding energy, the fusion evaporation residue yields for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ systems are almost the same, confirming the independence of the way in which the compound nucleus ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$ is formed. (ii) The systems ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ have been studied at $E_{\mathrm{lab}}=40\mathrm{}$ MeV. This energy corresponds approximately to the maxima of the fusion evaporation cross sections for all these systems. The yields to final residual nuclei show that the additional neutrons strongly affect mainly the $\alpha \mathrm{xn}$ and $2\alpha \mathrm{xn}$ channels and this is well reproduced by the Hauser-Feshbach statistical model. The results are compared to those obtained for neighboring fusion-evaporation systems.