Resonant characteristics of statistical fluctuations in 12C+12C reaction cross sections.

Abstract

The effects of angular momentum conservation on the properties of Ericson fluctuations in cross sections for the [sup 12]C([sup 12]C,[sup 8]Be[sub 0])[sup 16]O(g.s.) reaction and [sup 12]C([sup 12]C,[alpha])[sup 20]Ne[sup *] reactions leading to the 12 lowest excitations in [sup 20]Ne are studied. Comparison of Hauser-Feshbach predictions to experimental measurements of the [sup 8]Be[sub 0] total cross section in the range 9[le][ital E][sub c.m.][le]20 MeV indicates that this reaction channel is populated primarily by a compound-nucleus mechanism. Similar results are obtained for the majority of the [alpha]-particle channels in the energy region from [ital E][sub c.m.]=6.5 to 12.6 MeV. The compound-nucleus cross sections for these reactions are dominated by a narrow range of angular momenta. A statistical model that includes predicted unequal contributions from compound-nucleus levels with different spins is used to synthesize angular distributions and excitation functions for comparison to data. The results of these simulations give overall quantitatively correct estimates of the size and frequency of the fluctuations observed in the measured total cross sections and of the spins that dominate the fluctuations. Consequences for the identification of resonances'' are discussed.