Parity dependence of the level densities ofCr53andCr55at high excitation

The neutron total cross sections of ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$ and ${}_{}{}^{54}{}_{}{}^{}\mathrm{Cr}$ have been measured in the energy range from a few tens of keV to about 900 keV using a neutron time-of-flight technique and a pulsed electron linear accelerator. The nominal resolution of the measurements was about 0.06 ns/m. The total cross-section data have been analyzed using an $R$-matrix multilevel multichannel code to determine values of the resonance parameters ($E_0$, $g{\Gamma }_{\mathrm{n}}$, and $J^{\pi }$) and to investigate the parity dependence of the level densities of ${}_{}{}^{53}{}_{}{}^{}\mathrm{Cr}$ and ${}_{}{}^{55}{}_{}{}^{}\mathrm{Cr}$ at high excitation. From these analyses we obtain the following values for the average properties of the resonance parameters for $s$-wave resonances up to about 900 keV and for $p$-wave resonances up to 600 keV: $D_0=(45\mathrm{}\pm 6)$ keV, $S_0(\times {10}^4)=(3.0\mathrm{}\pm 1.0)$, $D_1=(8.5\mathrm{}\pm 0.6)$ keV, $S_1(\times {10}^4)=(0.70\mathrm{}\pm 0.12)$ for ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$; and $D_0=(60\mathrm{}\pm 9)$ keV, $S_0(\times {10}^4)=(2.6\mathrm{}\pm 0.9)$, $D_1=(9.2\mathrm{}\pm 0.5)$ keV, $S_1(\times {10}^4)=(0.67\mathrm{}\pm 0.11)$ for ${}_{}{}^{54}{}_{}{}^{}\mathrm{Cr}$. The distributions of reduced neutron widths for $s$- and $p$-wave resonances for each isotope show good agreement with the Porter-Thomas distribution. The values of the ${\Delta }_3$ statistic for the long-range correlation of $s$-wave resonances for both ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$ and ${}_{}{}^{54}{}_{}{}^{}\mathrm{Cr}$ and found to be in reasonable agreement with the theoretical prediction of Dyson and Metha. The values for the ratio $\frac{D_0}{D_1}$ for both nuclides are larger than expected from a ($2J+1$) level dependence, indicative of a parity dependence of the level densities of ${}_{}{}^{53}{}_{}{}^{}\mathrm{Cr}$ and ${}_{}{}^{55}{}_{}{}^{}\mathrm{Cr}$ at high excitation.