Parity dependence of the nuclear level density at high excitation

Abstract

Abstract The basic underlying assumption ϱ(l + 1, J) = ϱ(l, J) in the level density function π(U, J, π) has been checked on the basis of high quality data available on individual resonance parameters (E0, Γn, Jπ) for s- and p-wave neutrons in contrast to the earlier analysis where information about p-wave resonance parameters was meagre. The missing level estimator based on the partial integration over a Porter-Thomas distribution of neutron reduced widths and the Dyson-Mehta Δ3 statistic for the level spacing have been used to ascertain that the s- and p-wave resonance level spacings D(0) and D(1) are not in error because of spurious and missing levels. The present work does not validate the tacit assumption π(l + 1, J) = π(l, J) and confirms that the level density depends upon parity at high excitation. The possible implications of the parity dependence of the level density on the results of statistical model calculations of nuclear reaction cross sections as well as on pre-compound emission have been emphasized.