Activation cross section and isomeric cross-section ratio for the 93Nb(n, alpha )90Ym,g process.

Abstract

Cross sections were measured for the $^{93}\mathrm{Nb}$(n,\ensuremath{\alpha}${)}^{90}$${\mathrm{Y}}^{\mathrm{m}}$, $^{93}\mathrm{Nb}$(n,${\ensuremath{\alpha}}^{90}$${\mathrm{Y}}^{\mathrm{m}+\mathrm{g}}$, and $^{93}\mathrm{Nb}$(n,2n${)}^{92}$${\mathrm{Nb}}^{\mathrm{m}}$ reactions from threshold up to 10.6 MeV. Use was made of the activation technique in combination with high-resolution \ensuremath{\gamma}-ray spectroscopy, except for the product $^{90}\mathrm{Y}^{\mathrm{g}}$ where radiochemical separation and ${\ensuremath{\beta}}^{\mathrm{\ensuremath{-}}}$ ray counting were applied. The quasi-monoenergetic neutrons were produced via the $^{2}\mathrm{H}$(d,n${)}^{3}$He reaction using a deuterium gas target at a compact cyclotron. Statistical model calculations taking into account precompound effects (reported in the literature) agree reasonably well with the experimental excitation functions for the formation of both $^{90}\mathrm{Y}^{\mathrm{m}}$ and $^{90}\mathrm{Y}^{\mathrm{m}+\mathrm{g}}$. The isomeric cross-section ratio for the $^{93}\mathrm{Nb}$(n,\ensuremath{\alpha}${)}^{90}$${\mathrm{Y}}^{\mathrm{m}}$,g reactions increases with energy. The model calculation gives somewhat lower values for the ratio.