First observation of excited states in theTz=1/2nucleus85Mo

Abstract

Excited states in the ${T}_{z}=\frac{1}{2}$ nucleus ${}^{85}\mathrm{Mo}$ have been observed for the first time with the reaction ${}^{58}\mathrm{Ni}{(}^{32}\mathrm{S},\ensuremath{\alpha}n\ensuremath{\gamma})$ at 105 MeV. $\ensuremath{\gamma}$-ray transitions in this nucleus have been assigned unambiguously by combining the information from the GASP $\ensuremath{\gamma}$-ray array, the ISIS silicon ball, and the n-Ring neutron detector. Two band structures have been observed in this nucleus; they continue the smooth evolution of the known bands from the lighter $N=43$ isotones and have been tentatively assigned spins and parity on this basis. After reaching a maximum of collectivity at ${}^{83}\mathrm{Zr},$ the trend with increasing mass is reversed, showing a smaller collectivity at ${}^{85}\mathrm{Mo}.$ The rotational behavior of the observed bands is discussed on the basis of the projected shell model calculations.