COMPOUND NUCLEAR LIFETIMES AT HIGH-EXCITATION ENERGIES VIA A NEW STATISTICAL FLUCTUATION METHOD

A new method to determine compound nuclear lifetimes at high excitatio n energies is proposed and applied to the system C-12(Si-28, alpha)Ar- 36 at two different bombarding energies, 190 and 277 MeV. The alpha pa rticle spectra show a structure which directly reflects the fluctuatin g behavior of the first de-excitation step. Coherence widths and thus lifetimes for the nucleus Ar-36 were obtained via a correlation functi on analysis. The results at low excitation energies are consistent wit h standard statistical models while the result at high excitation ener gy is compatible with a theoretically predicted change of the level de nsity parameter. (C) 1998 Published by Elsevier Science B.V. All right s reserved.