Production and characterization of hot nuclei in the reactions of 19 and 35 MeV/u 14N with 145Sm

Abstract

Hot nuclei produced in the reactions of 261 MeV and 490 MeV 14N with 154Sm have been studied. The initial properties of these nuclei; excitation energies, angular momenta and temperatures, have been characterized through measurements of residue velocities, gamma ray multiplicities and α-particle energy spectra. Nuclei with excitation energies as high as 400 MeV and temperatures as high as 6 MeV are produced. Determinations of the variation of temperature with excitation energy for nuclei of A ⋍ 160 indicate that the apparent level density parameter a, defined as E ∗|T 2 changes from A/8 at low energies to ≈ A/13 at 400 MeV excitation energy. Effective particle emission barriers suggest large shape fluctuations during the de-excitation cascade. At 35 MeV/u the variation of angular momentum transfer with linear momentum transfer in incomplete fusion reactions is in reasonable agreement with values calculated using a geometric overlap model.