Two-step γ cascades following thermal neutron capture inMo95

Abstract

A strong enhancement of the photon strength function at low \ensuremath{\gamma}-ray energies was recently reported for several Mo isotopes. To study this enhancement further we have measured the spectra of two-step \ensuremath{\gamma} cascades following thermal neutron capture in $^{95}\mathrm{Mo}$. These spectra were compared with simulations of the \ensuremath{\gamma} decay of $^{96}\mathrm{Mo}$ performed with the aid of the dicebox algorithm. Simulations with a large number of model combinations of photon strength functions for $E1,M1,$ and $E2$ radiation are not consistent with the strong enhancement observed in the $^{96}\mathrm{Mo}$($^{3}\mathrm{He}$,$^{3}\mathrm{He}$${}^{'}\ensuremath{\gamma}$)$^{96}\mathrm{Mo}$ and $^{97}\mathrm{Mo}$($^{3}\mathrm{He}$,$\ensuremath{\alpha}\ensuremath{\gamma})$$^{96}\mathrm{Mo}$ reactions. Predictions based on a combination of $E1,M1,$ and $E2$ photon strength functions with no enhancement of the photon strength functions at low \ensuremath{\gamma}-ray energies are in good agreement with the two-step \ensuremath{\gamma} cascade data.