Does the $\alpha $ Cluster Structure in Light Nuclei Persist Through the Fusion Process?

Despite the importance of light-ion fusion in nucleosynthesis, a limited amount of data exist regarding the de-excitation following fusion for such systems. The characteristics of $\alpha$ emission following the fusion of $^{18}$O and $^{12}$C nuclei have been explored. Alpha particles were detected in coincidence with evaporation residues (ER) and identified on the basis of their energy and time-of-flight. ERs were characterized by their energy spectra and angular distributions while the $\alpha$ particles were characterized by their energy spectra, angular distributions, and cross-sections. While the energy spectra and angular distributions for the $\alpha$ particles are relatively well reproduced by statistical model codes, the measured cross-section is substantially underpredicted by the models. Comparison of the measured relative $\alpha$ cross-section at low E$_{c.m.}$ for $^{18}$O+$^{12}$C, $^{16}$O+$^{12}$C, and $^{16}$O+$^{13}$C indicates that the $\alpha$ cluster structure of the initial projectile and target nuclei influences the $\alpha$ emission following fusion. The underprediction of the relative $\alpha$ emission by the statistical model codes suggests that the failure of these models to account for $\alpha$ cluster structure is significant.