Pairing corrections and spin cutoff factors in exciton level densities for two kinds of fermions

Journal Article · Sun Sep 01 04:00:00 EDT 1991 · Nuclear Science and Engineering; (United States)

OSTI ID:5525716

Fu, C Y ^[1]

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1. Oak Ridge National Lab., Oak Ridge, TN (US)

Pairing corrections in particle-hole (exciton) state-density formulas used in precompound nuclear reaction theories are, strictly speaking, dependent on the nuclear excitation energy U and the exciton number n. A general formula for (U, n)-dependent pairing corrections was derived earlier for the exciton state-density formula for a system of one kind of fermion. A similar derivation is made for a system of two kinds of fermions, a system in which neutrons and protons occupy different sets of single-particle states. In this paper it is shown that the constant-pairing- energy correction used in standard state-density formulas, such as U{sub 0} in Gilbert and Cameron, is a limiting case of the present general (U,n)-dependent results. Spin cutoff factors are calculated using the same pairing theory and parameterized into an explicit (U,n)-dependent function, thereby defining the exciton level-density formula for two kinds of fermions. The results show that the ratios in the exciton level densities in the one-and two-fermion approaches vary with both U and n, thus, most likely leading to differences in calculated compound-to-precompound ratios. However, the differences in the spin cutoff factors in the two cases are found to be rather small.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5525716
• Journal Information: Nuclear Science and Engineering; (United States), Journal Name: Nuclear Science and Engineering; (United States) Vol. 109:1; ISSN 0029-5639; ISSN NSENA
• Country of Publication: United States
• Language: English

Related Subjects

663110* -- General & Average Properties of Nuclei & Nuclear Energy Levels-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANGULAR MOMENTUM
CALCULATION METHODS
CROSS SECTIONS
ENERGY LEVELS
ENERGY-LEVEL DENSITY
EXCITATION FUNCTIONS
EXCITED STATES
EXCITON MODEL
EXCITONS
FERMIONS
FUNCTIONS
INTERACTIONS
MATHEMATICAL MODELS
NUCLEAR MODELS
NUCLEAR REACTIONS
PAIRING INTERACTIONS
PARTICLE MODELS
PARTICLE PROPERTIES
QUASI PARTICLES
SINGLE-PARTICLE MODEL
SPIN