Magnetic Moment of the Fragmentation Aligned 61Fe(9/2)+ Isomer

Abstract

We report on the g factor measurement of the isomer in ${}^{61}Fe$ ($E^{\ast }=861keV$). The isomer was produced and spin-aligned via a projectile-fragmentation reaction at intermediate energy, the Time Dependent Perturbed Angular Distribution (TDPAD) method being used for the measurement of the g factor. For the first time, due to significant improvements of the experimental technique, an appreciable residual alignment of the isomer has been observed, allowing a precise determination of its g factor: $g=-0.229(2)$. Comparison of the experimental g factor with shell-model and mean field calculations confirms the $9/2^{+}$ spin and parity assignments and suggests the onset of deformation due to the intrusion of Nilsson orbitals emerging from the $\hat{I}½g_{9/2}$.

4 figures. Submitted to Phys. Rev. Lett