Nuclear-Structure and Hyperfine-Field Studies withMo95

Abstract

Excitation functions for ($\alpha ,xn$), ($\alpha ,\alpha n$), and ($\alpha ,2p$) reactions upon niobium targets have been measured for incident $\alpha$-particle energies from 15 to 41 MeV Excited states in ${\mathrm{Mo}}^{95}$ have been studied by observing the decay of the 61-day isotope ${\mathrm{Tc}}^{95m}$, which was produced by the ${\mathrm{Nb}}^{93}(\alpha ,2n)$ reaction. The energies and the intensities of the $\gamma$ rays resulting from this decay have been measured. The angular-correlation coefficients of the two strongest cascades in ${\mathrm{Mo}}^{95}$ have been found to be $A_{22}=-0.292\mathrm{}\pm 0.005$ and $A_{44}=-0.001\mathrm{}\pm 0.006$ for the 582-204-keV cascade, and $A_{22}=-0.196\mathrm{}\pm 0.006$ and $A_{44}=-0.003\mathrm{}\pm 0.008$ for the 835-204-keV cascade. The mean life of the 204-keV state has been measured by the delayed-coincidence technique and found to be 1.09 ± 0.02 nsec. The $g$ factor of the 204-keV state has been measured to be -0.26 ± 0.02. A summary of a number of calculations concerning the nuclear structure of ${\mathrm{Mo}}^{95}$ is given, and some predictions of the Kisslinger-Kumar model of near-spherical nuclei for ${\mathrm{Mo}}^{95}$ are presented. The technique of perturbed angular correlations has been used to measure the hyperfine fields at the molybdenum nucleus in iron and nickel hosts. These fields have been found to be ${\mathrm{B}}_{\mathrm{e}\mathrm{f}\mathrm{f}}\left(\mathrm{Mo}\mathrm{in}\mathrm{Fe}\right)=-236\mathrm{}\pm 19$ kG and ${\mathrm{B}}_{\mathrm{e}\mathrm{f}\mathrm{f}}\left(\mathrm{Mo}\mathrm{in}\mathrm{Ni}\right)=-29.9\mathrm{}\pm 5.1$ kG at 55°C.