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Phys. Rev. C 66, 014608 (2002) [16 pages]

Near-scission emission of intermediate mass fragments in 12C+232Th at E/A=16 and 22 MeV

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T. A. Bredeweg, R. Yanez*, B. P. Davin, K. Kwiatkowski†, and R. T. de Souza
Department of Chemistry and Indiana University Cyclotron Facility, Indiana University, Bloomington, Indiana 47405

R. Lemmon‡ and R. Popescu§
National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824

R. J. Charity and L. G. Sobotka
Department of Chemistry, Washington University, St. Louis, Missouri 63130

D. Hofman**
Physics Division, Argonne National Laboratory, Argonne, Illinois 60439

N. Carjan
Centre d’Etudes Nucléaires de Bordeaux-Gradignan, BP 120, F-33175 Gradignan Cedex, France

Received 25 July 2001; published 17 July 2002

Intermediate mass fragments (IMFS) (IMF: 3<~ZIMF<~20) observed in coincidence with two correlated fission fragments following incomplete fusion in 12C+232Th at E/A=16 and 22 MeV are investigated. IMFs emitted prior to significant deformation of the fissioning system, as well as IMFs emitted near scission, are distinguished based upon their characteristic kinetic energy and angular distributions. The yield distributions of IMFs emitted near scission in these12C induced reactions are compared with near-scission IMF yields in spontaneous and low-energy ternary fission. Comparisons are made to both experimental fusion-evaporation data and theoretical predictions of a statistical model. The excitation energy dependence of relative IMF yields for both isotropic and near-scission emission is also presented. Our results for near-scission emission suggest that the production of IMFs near scission is inconsistent with a statistical emission mechanism in which emission barriers follow a standard Z dependence. Dynamical model calculations are used to investigate the role of dissipation, angular momentum, N/Z, and kinetic energy on the fragment formation near scission.

© 2002 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevC.66.014608
DOI:
10.1103/PhysRevC.66.014608
PACS:
25.70.Jj, 25.85.Ge, 47.20.Dr

*Present address: Universidad de Chile, Santiago, Chile.

†Present address: Los Alamos National Lab., Los Alamos, NM.

‡Present address: CCLRC Daresbury Laboratory, Warrington, WA4 4AD UK.

§Present address: Brookhaven National Laboratory, Upton, NY.

**Present address: University of Illinois at Chicago, Chicago, IL.

 
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