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

Journal Article · Fri Oct 01 00:00:00 EDT 1993 · Physical Review, C (Nuclear Physics); (United States)

DOI:https://doi.org/10.1103/PhysRevC.48.1667· OSTI ID:6109356

Ohtsuki, T ^[1]; Nakahara, H ^[2]; Nagame, Y ^[3]

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1. Laboratory of Nuclear Science, Faculty of Science, Tohoku University, Mikamine, Taihaku, Sendai, 982 (Japan)
2. Department of Chemistry, Faculty of Science, Tokyo Metropolitan University, Minami-Ohsawa, Hachioji, Tokyo, 192-03 (Japan)
3. Japan Atomic Energy Research Institute (JAERI), Tokai, Ibaraki, 319-11 (Japan)

The excitation functions and the mass yield curves for proton-induced fissions of [sup 233]U, [sup 235]U, [sup 236]U, [sup 237]Np, [sup 239]Pu, [sup 242]Pu, [sup 244]Pu, [sup 241]Am, and [sup 243]Am 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 [ital A][sub [ital f]] 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 [ital A][sub [ital f]]=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 [ital N][similar to]150, neutron number of the fissioning nuclide, to a large negative value for [ital N][similar to]126, and the two barrier heights become comparable at [ital N]=135--138.

• OSTI ID: 6109356
• Journal Information: Physical Review, C (Nuclear Physics); (United States), Vol. 48:4; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
FISSION
EXCITATION FUNCTIONS
FISSION BARRIER
STATISTICAL MODELS
BOHR-WHEELER THEORY
DATA ANALYSIS
ENERGY-LEVEL DENSITY
FISSION YIELD
SYMMETRY
CROSS SECTIONS
FUNCTIONS
MATHEMATICAL MODELS
NUCLEAR POTENTIAL
NUCLEAR REACTION YIELD
NUCLEAR REACTIONS
POTENTIALS
YIELDS
663470* - Fission- (1992-)
663590 - Nuclear Mass Ranges- A=220 & Above- (1992-)