Valency Neutron Capture inMo92(n,γ)Mo93

Abstract

Capture $\gamma$-ray spectra from the ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}(n,\gamma ){}_{}{}^{93}{}_{}{}^{}\mathrm{Mo}$ reaction were measured for neutron energies below 100 keV using the 10-m flight path at the Oak Ridge electron linear accelerator. For neutron energies less than 25 keV a total of 23 different $s$- and $p$-wave resonances were resolved. The neutron binding energy is 8067.4± 1.5 keV. The partial radiation widths for the 12 highest energy $\gamma$ rays which populate positive-parity states below 2.5-MeV excitation were deduced and compared to the valency-model predictions of Lane and Lynn. For $\gamma$-ray energies less than 6.5 MeV, the average $M1\mathrm{}$ partial radiation width is approximately equal to the average $E1\mathrm{}$ partial radiation width. The reduced transition strengths as defined by Bartholomew for these transitions are $\overline{k}\mathrm{}\left(E1\mathrm{}\right)=(1.2\mathrm{}\pm 0.2)\times {10}^{-3\mathrm{}}$ and $\overline{k}\mathrm{}\left(M1\mathrm{}\right)=(11.5\mathrm{}\pm 2.3)\times {10}^{-3\mathrm{}}$. For the 7126-keV transition to the $s_{\frac{1}{2}}$ first excited state the average reduced strength is enhanced by a factor of 5 and 2 for the $E1\mathrm{}$ and $M1\mathrm{}$ transitions, respectively. Nearly 30% of this enhancement for the $E1\mathrm{}$ multipoles is attributed to the valency-model contribution while the remainder is assigned to other processes such as the giant dipole resonance and doorway-state components. The average $E2\mathrm{}$ width for the 8067-keV ground-state $\gamma$ rays is approximately 10% of the average $E1\mathrm{}$ ground-state width.