Magnetic moment of the 11/2− isomeric state in Mo99 and neutron spin g factor quenching in A≈100 nuclei

The gyromagnetic factor of the low-lying Ex=684.10(19)keV isomeric state of the nucleus 99Mo was measured using the time-dependent perturbed angular distribution technique. This level is assigned a spin and parity of Jπ=11/2−, with a half-life of T1/2=742(13)ns. The state of interest was populated and spin-aligned via a single-neutron transfer on a highly enriched 98Mo target. A magnetic moment μexpt.=−0.627(20)μN was obtained. This result is far from the Schmidt value expected for a pure single-particle νh11/2 state. A comparison of experimental spectroscopic properties of this nucleus is made with results of multishell Interacting boson-fermion Model (IBFM-1) calculations. In this approach, the Jπ=11/2− isomeric state in 99Mo has a pure νh11/2 configuration. Its magnetic moment, as well as that of other two excited states could be reasonably well reproduced by reducing the free neutron spin g factor with a quenching factor of 0.45. This low value is not appropriate only for this case, similar values for the quenching factor being also required in order to describe magnetic moments in other nuclei from the same mass region