FLUCTUATIONS IN THE C$sup 12$(O$sup 16$,/cap alpha/)Mg$sup 24$ REACTION

Abstract

Rapid fluctuations were observed in the excitation functions at two angles for C/sup 12/(O/sup 16/, alpha )Mg/sup 24/ reactions involving the low- lying states of Mg/sup 24/. The energy resolution in the entrance channel was 45 kev. The fluctuations were found at compound-nucleus excitation energies of about 2 plus or minus and 30 Mev. At 30 Mev they were as strong as at 2 plus or minus Mev. The statistical theory of Ericson was applied and autocorrelation functions were used to determine the width of the fluctuations. The average width, approximately 116 kev, corresponds to a compound-nucleus lifetime of 0. plus or minus 7 x 10/sup -20/ sec. Cross correlations between different transitions are usually small, as predicted by the theory. Upper limits on the noncompound cross section are given for the ground state transition. A comparison is made with Al/sup 27/(p, alpha )Mg/sup 24/ results at the same angles and energies in the light of the statistical theory. Other possible interpretations of the experimental data are discussed. (auth)