Abstract
We have measured inclusive γ-ray production cross sections for and α-induced reactions on various targets in the mass range A=61–181 at projectile energies of 11–27 MeV. Except for α-induced yields on the lightest targets, all reactions show high-energy γ-ray yields 1–3 orders of magnitude larger than can be obtained from statistical model calculations. Angular distributions are strongly forward peaked in the center of mass frame for the highest γ-ray energies, providing model-independent evidence for a nonstatistical reaction mechanism. Calculations of direct radiative capture and semidirect excitation of the giant dipole resonance can qualitatively reproduce the angular distributions but cannot reproduce either the dependence of the γ-ray cross sections on or the target dependence of the absolute cross sections. The He,O reaction was found to change from predominantly statistical to predominantly direct over this bombarding energy range. © 1996 The American Physical Society.
- Received 21 September 1995
DOI:https://doi.org/10.1103/PhysRevC.53.1759
©1996 American Physical Society