High-resolution transmission measurements forCr54+n

Abstract

Neutron total cross-section measurements on $^{54}\mathrm{Cr}$ up to a neutron energy of 2 MeV have been analyzed to deduce resonance parameters as well as spins and parities. Neutron strength functions have been deduced, based on data in the energy range 20--1000 keV, for $s$-, $p$-, and $d$-wave interactions and, in units of (${10}^{\ensuremath{-}4}$), are $2.8\ifmmode\pm\else\textpm\fi{}0.9$, $0.23\ifmmode\pm\else\textpm\fi{}0.06$, and $4.4\ifmmode\pm\else\textpm\fi{}0.7$, respectively. Corresponding level densities in units of ${\mathrm{keV}}^{\ensuremath{-}1}$are $0.025\ifmmode\pm\else\textpm\fi{}0.003$, $0.032\ifmmode\pm\else\textpm\fi{}0.003$, and $0.107\ifmmode\pm\else\textpm\fi{}0.006$, respectively. The distribution of nearest-neighbor spacings for $s$ waves has been compared to Poisson and Wigner predictions for both $^{54}\mathrm{Cr}$ and $^{52}\mathrm{Cr}$. Hints are seen of greater chaotic behavior in the case of the closed-neutron-shell $^{52}\mathrm{Cr}$ and of regular dynamics for $^{54}\mathrm{Cr}$, suggestive of changes in chaoticity of nuclear dynamics with shell closure.