Isomeric to ground state ratio in the ${}^{180}{\mathrm{Ta}}^m(\gamma ,{\gamma }^{\prime }{)}^{180}{\mathrm{Ta}}^{m,g}$ reaction

The yield $Y$ of the ${}^{180}{\mathrm{Ta}}^m(\gamma ,{\gamma }^{\prime }{)}^{180}{\mathrm{Ta}}^g$ ($T_{1/2}=8.15\mathrm{}\hspace{0.5em}\mathrm{h}$) reaction has been measured as a function of the bremsstrahlung end-point energy $E_e$ in the range of 2.5–7.6 MeV. An activation technique was used for the yield measurement which was calibrated by monitoring the ${}^{232}\mathrm{Th}(\gamma ,f)$ reaction yield. The ${Y(E}_e)$ function was numerically simulated and the probability ${\sigma }_g/({\sigma }_g+{\sigma }_m)$ for the depletion of the ${}^{180}{\mathrm{Ta}}^m$ isomer after $\gamma$-ray absorption was deduced. This probability is important for astrophysical questions and schemes for producing induced γ emission and perhaps a $\gamma$-ray laser.