Systematic variation of fission barrier heights for symmetric and asymmetric mass divisions

T. Ohtsuki, H. Nakahara, and Y. Nagame
Phys. Rev. C 48, 1667 – Published 1 October 1993
PDFExport Citation

Abstract

The excitation functions and the mass yield curves for proton-induced fissions of U233, U235, U236, Np237, Pu239, Pu242, Pu244, Am241, and Am243 targets were studied. The excitation functions for near-symmetrically divided fragments were found quite different in shapes and threshold energies from those of asymmetrically divided ones in all the fissioning systems studied. In order to obtain the fission barrier heights for symmetric and asymmetric mass division, the conventional Bohr-Wheeler type calculations for the competition between fission and neutron emission were performed. In the calculation, two independent fission channels, symmetric and asymmetric, were assumed, and fission barrier heights and level density parameters that could best reproduce the shapes of the excitation functions (incident energy dependence) of typical symmetric and asymmetric products were deduced. Barrier heights for symmetric and asymmetric mass divisions both decrease as the mass of fissioning nuclide Af increases, and they also exhibit slight dependence on the atomic number. Difference between the two barrier heights is 2.0–2.5 MeV in the region of Af=236–245. From similar analysis of excitation function data reported in literature, it is found that the difference changes from a large positive value for N∼150, neutron number of the fissioning nuclide, to a large negative value for N∼126, and the two barrier heights become comparable at N=135–138.

  • Received 2 April 1993

DOI:https://doi.org/10.1103/PhysRevC.48.1667

©1993 American Physical Society

Authors & Affiliations

T. Ohtsuki

  • Laboratory of Nuclear Science, Faculty of Science, Tohoku University, Mikamine, Taihaku, Sendai, 982 Japan

H. Nakahara

  • Department of Chemistry, Faculty of Science, Tokyo Metropolitan University, Minami-Ohsawa, Hachioji, Tokyo, 192-03 Japan

Y. Nagame

  • Japan Atomic Energy Research Institute (JAERI), Tokai, Ibaraki, 319-11 Japan

References (Subscription Required)

Click to Expand
Issue

Vol. 48, Iss. 4 — October 1993

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
×