Background: Measurement of the energy dependence of the fusion cross-section at sub-barrier energies provides an important test for theoretical models of fusion.

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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 α 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 18 O and 12 C nuclei. Both α 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 α particles were characterized by their energy spectra, angular distributions, and cross-sections.Results: While the energy spectra and angular distributions for the α particles are relatively well reproduced by the statistical model codes, EVAPOR and PACE4, the measured cross-section is substantially underpredicted by the models. Examination of the relative α emission probability for similar systems reveals that this underprediction is a more general feature of such light-ion reactions. Conclusion:Comparison of the measured relative α cross-section at low Ec.m. for18 O + 12 C, 16 O + 12 C, and 16 O + 13 C indicates that the α cluster structure of the initial projectile and target nuclei influences the α emission following fusion. The underprediction of the relative α emission by the statistical model codes emphasizes that the failure of these models to account for α cluster structure is significant.

We report the first measurement of the fusion excitation functions for 39,47 K + 28 Si at nearbarrier energies. Evaporation residues resulting from the fusion process were identified by direct measurement of their energy and time-of-flight with high geometric efficiency. At the lowest incident energy, the cross-section measured for the neutron-rich 47 K induced reaction is ∼6 times larger than that of the β-stable system. This experimental approach, both in measurement and analysis, demonstrates how to efficiently measure fusion with low-intensity, re-accelerated radioactive beams, establishing the framework for future studies.

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