  [Background] Despite the importance of light-ion fusion in nucleosynthesis, a
limited amount of data exists regarding the de-excitation following fusion for
such systems. [Purpose] To explore the characteristics of alpha emission
associated with the decay of light fused systems at low excitation energy.
[Method] Alpha particles were detected in coincidence with evaporation residues
(ER) formed by the fusion of 18O and 12C nuclei. Both alpha particles and ERs
were 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. [Results] While the energy spectra and angular
distributions for the alpha particles are well reproduced by statistical model
codes, the measured cross-section is substantially underpredicted by the
models. Comparison with similar systems reveals that the fundamental quantity
for the alpha cross-section is Ec.m. and not the excitation energy of the fused
system. [Conclusion]The enhancement in the measured alpha cross-section as
compared to the statistical model codes and its dependence with Ec.m. suggest
that a coupling between pre-existing alpha cluster structure and the collision
dynamics is responsible for the observed alpha cross-section.
