Spin assignments for quasi-molecular resonances from angular correlation techniques

Abstract

-IntroductionThe study of resonances in the scattering of 12 C+ 12 C attracted a great deal of attention some years ago, with the association of peaks in the excitation functions for scattering and transfer reactions in this system with quasi-molecular structures in the composite nucleus 24 Mg [1,2]. Resonances in this system have been linked to extended, deformed cluster configurations in 24 Mg at high excitation energy [3], but reaction models are often able to reproduce at least the qualitative features of the data (e.g., [4]). Progress in the understanding of the nature of resonances in this and other systems has, however, often been hampered by the lack of precise experimental information. In many cases, resonances in the 12 C+ 12 C system appear in inelastic reaction channels where the channel spin is non-zero. The usual method of measuring inclusive scattering angular distributions thus becomes insensitive to the resonance spin due to the complications arising from the spin of the excited scattered heavy ion. As a result, few rigorous spin assignments have been available for resonances in inelastic scattering channels with non-zero channel spin. Some progress was made by resorting to particle-gamma-ray angular correlation measurements [5][6][7], however definitive measurements are complicated and, without a 4-gamma-detector apparatus, the results are often model dependent and difficult to interpret.