Parity dependence of nuclear level densities

Abstract

High resolution proton resonance data have been examined for a possible parity dependence of nuclear level densities. Five spin-parity ${\mathrm{combinations}\mathrm{---}1/2}^{+},$ ${1/2}^{\ensuremath{-}},$ ${3/2}^{\ensuremath{-}},$ ${3/2}^{+},$ and ${5/2}^{+}$---have been analyzed for three ${\mathrm{datasets}\mathrm{---}}^{44}\mathrm{Ca}(p,p),$ ${}^{48}\mathrm{Ti}(p,p),$ and ${}^{56}\mathrm{Fe}(p,p).$ Much of the uncertainty in the level density arises from the determination of the fraction of levels that are not observed. The missing fraction of levels was determined by (a) the standard width analysis method that assumes a Porter-Thomas distribution for the reduced widths and (b) a recently developed method that analyzes the spacing distribution and assumes the Wigner distribution for the nearest-neighbor spacings. There are indications of parity dependence of the level densities for several of the spin-parity combinations.