Light-charged-particle emission in the matched reactions 280 MeV 40Ar+27Al and 670 MeV 55Mn+12C: Coincidence results

Exclusive measurements of light-charged-particle (1H, 2H, and 4He) energy spectra, angular distributions, and emission multiplicities are reported for the two reactions 40Ar+27Al and 55Mn+12C at a matched excitation energy of 127 MeV. Comparisons are made with statistical model predictions for the evaporative processes in these reactions, which can be characterized as emissions from rotational-energy-dominated systems. The model simulations do well in reproducing a broad range of angular distribution data and the 4He/1H cross-section ratio, using spin distributions derived from fusion cross-section systematics. The same model parameters, however, predict particle energy spectra and coincidence cross sections which are inconsistent with the measurements for both reactions. These results support previous conclusions from model comparisons with inclusive data, and suggest fundamental flaws in the statistical model as applied to light-mass, high-spin, nuclear systems. (c) 2000 The American Physical Society