Slow Neutron Resonance Spectroscopy. II. Ag, Au, Ta

Abstract

The results of time-of-flight measurements of Ag, Au, and Ta resonance parameters are presented. Neutron widths are given for 79 levels in Ag to 728 ev, 55 levels in Au to 940 ev, and 62 levels in Ta to 330 ev. Radiation widths for many of the stronger levels, and in some cases resonance $J$ values are obtained. The reduced neutron width distributions are in good agreement with Porter-Thomas distributions for Au and Ta. The distribution for Ag shows a large excess of small ($2g{{\Gamma }_n}^0$) values which are interpreted as $p$-wave resonances and correspond to a $p$-wave strength function $S_1=(1.7\mathrm{}\pm 0.8)\times {10}^{-4\mathrm{}}$. The $s$-wave strength functions are (0.51±0.09)×${10}^{-4\mathrm{}}$ for Ag, (1.5±0.3)×${10}^{-4\mathrm{}}$ for Au, and (1.84±0.34)×${10}^{-4\mathrm{}}$ for Ta. The observation of $p$-wave Ag levels is interpreted as due to a $p_{\frac{1}{2}}$ strength function resonance in this region. The level spacing distributions for Au and Ta agree with the expected two-population Wigner spacing distribution function but not with random or single Wigner distributions. The weighted average ${\Gamma }_{\gamma }$ values are 0.148 ev, 0.170 ev, and 0.060 ev for Ag, Au, and Ta, respectively.