Neutron resonance spectroscopy. XV. The separated isotopes of Cd

Abstract

The results of neutron time of flight spectroscopy measurements for the separated Cd isotopes (110, 112, 114, 116) and for natural Cd, using the Nevis synchrocyclotron, are given. Transmission and self-indication measurements were made for a range of sample thicknesses for natural Cd, and for each of the above even A separated isotopes. Resonance parameters, ${\mathrm{E}}_0$ and $\mathrm{}\left(g\right)\mathrm{}{\Gamma }_n^0$ are given to ∼ 10 keV for 110, 112, 114, 116, and to 2.3 keV for 111 and 113. The ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$ level assignment is from recent published measurements at the Oak Ridge electron linear accelerator using a sample enriched in ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$. Levels in ${}_{}{}^{113}{}_{}{}^{}\mathrm{Cd}$ are those stronger ones seen in natural Cd, but not identified as due to other isotopes. We also obtained level parameters to ∼ 10 keV for 181 levels which have no isotopic assignment. Many resonance ${\Gamma }_{\gamma }$ and $J$ values were obtained for 111 and 113, and a few ${\Gamma }_{\gamma }$ values for even $A$ isotopes, with $〈{\Gamma }_{\gamma }〉$ of each isotope being between 100 and 110 meV. The ${10}^4{S}_0$ values are 0.50 ± 0.10, 0.38 ± 0.06, 0.53 ± 0.09, 0.43 ± 0.07, 0.70 ± 0.19, and 0.20 ± 0.06 for 110, 111, 112, 113, 114, and 116, respectively. Comparison of the ${\left(g{\Gamma }_n^0\right)}^{\frac{1}{2}}$ distributions with Porter-Thomas theory for 110, 112, 114, and 111 shows that many $p$ levels are observed. An estimate of the level detection sensitivity and a Bayes's theorem analysis permit us to identify the detected $p$ levels, and to determine the $p$ strength function with a relatively small uncertainty. Few expected missing weak $s$ levels for each of these isotopes were then added to their $p$ level subtracted sets. Various statistical tests were applied, showing that the final $s$ level selection choices for 110, 112, 114 and 111 are in good agreement with the orthogonal ensemble theory. The ${10}^4{S}_1$ values for 110, 112, 114, and 111 are 2.8 ± 0.6, 2.5 ± 0.5, 3.2 ± 1.0, and 3.5 ± 0.7. The $〈D〉$ values for $s$ population are (174 ± 18) eV (110); (24.0 ± 1.5) eV (11); (137 ± 8) eV (112); (22.1 ± 3.8) eV (113); (183 ± 29) eV (114); and (264 ± 38) eV (116).