Temperature and np asymmetry dependencies of the level-density parameter in Ni+Mo fusion reactions

R. J. Charity, L. G. Sobotka, J. F. Dempsey, M. Devlin, S. Komarov, D. G. Sarantites, A. L. Caraley, R. T. deSouza, W. Loveland, D. Peterson, B. B. Back, C. N. Davids, and D. Seweryniak
Phys. Rev. C 67, 044611 – Published 29 April 2003
PDFExport Citation

Abstract

Properties of evaporation residues and the accompanying light particles have been measured in 60Ni+92,100Mo fusion reactions at bombarding energies from E/A=5 to 9 MeV. The data indicate that these reactions are essentially complete-fusion reactions with only a small amount of nonequilibrium emission at the highest bombarding energy studied. The measured kinetic-energy spectra of evaporated n, p, d, t, 3He, and α particles are compared to statistical-model predictions. It is found that a constant excitation-energy independent level-density parameter is not able to reproduce these spectra over the compound-nucleus excitation-energy range from 90 to 250 MeV. The kinetic-energy spectra for all particles were fit using the level-density parametrization a=A/(7+1.3×U/A)MeV1, where U is the thermal excitation energy. The Coulomb barriers for charged-particle emission were reduced from the standard values to reproduce the peak energy and multiplicity for α particles. Using these ingredients, the measured mass, velocity, and angular distributions of evaporation residues are also reproduced. The average Z and N of the evaporation residues deduced from the light-particle multiplicities are in agreement with the predicted location of the evaporation attractor line. A neutron-proton asymmetry dependence of the level-density parameter is shown to have potentially important consequences for the neutron or proton richness of the evaporation residues. However, no evidence for such an effect is found in the measured data; and from the experimental multiplicity ratio of t/3He it was deduced that any such dependence in the excitation-energy regime 100<E*<250MeV is very small.

  • Received 12 January 2003

DOI:https://doi.org/10.1103/PhysRevC.67.044611

©2003 American Physical Society

Authors & Affiliations

R. J. Charity*, L. G. Sobotka, J. F. Dempsey, M. Devlin, S. Komarov, and D. G. Sarantites

  • Department of Chemistry, Washington University, St. Louis, Missouri 63130

A. L. Caraley§ and R. T. deSouza

  • Department of Chemistry, Indiana University, Bloomington, Indiana 47401

W. Loveland and D. Peterson

  • Department of Chemistry, Oregon State University, Corvallis, Oregon 97331

B. B. Back, C. N. Davids, and D. Seweryniak

  • Physics Division, Argonne National Laboratory, Argonne, Illinois 60439

  • *Email address: charity@wuchem.wustl.edu
  • Present address: Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, FL 32610.
  • Present address: LANSCE-3, Los Alamos National Laboratory, Los Alamos, NM 87545.
  • §Present address: Department of Physics, State University of New York at Oswego, Oswego, NY 13126.

References (Subscription Required)

Click to Expand
Issue

Vol. 67, Iss. 4 — April 2003

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review C

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×