Neutron Resonance Spectroscopy. VI. Mo, Sb, Te, and Pr

The total neutron cross sections of natural Mo, Te, Sb, and Pr have been measured from about 6 eV to a maximum energy of 250 keV for Mo and Pr and to about 5 keV for Sb and Te, using the Nevis synchrocyclotron and a 200-m flight path. The maximum time resolution is 0.5 nsec/m. The resonance energies and the neutron reduced widths of about 1000 levels have been obtained, using area analysis. Values of ${\Gamma }_{\gamma }\sim 100$ meV were obtained for the capture widths of 15 levels in natural Sb. Values of the spin $J$ of the compound nucleus were obtained for a number of levels of Pr. Our values for the $s$-wave strength function for Mo, Sb, Te, and Pr are $S_0=(0.35\mathrm{}\pm 0.06), (0.34\mathrm{}\pm 0.05), (0.15\mathrm{}\pm 0.03), \mathrm{and} (1.72\mathrm{}\pm 0.25)\times {10}^{-4\mathrm{}}$, respectively. An average level spacing $〈D〉=75.2\mathrm{}$ eV was obtained for Pr. The presence of many $p$-wave levels led to a strong energy dependence of the observed $〈D〉$ for Mo, Sb, and Te. The observed statistical distributions of the neutron reduced widths and nearest-neighbor level spacings for Pr and natural Sb are compared with the Porter-Thomas and Wigner distributions, respectively.