Decay properties of neutron-rich niobium isotopes

Abstract

The decay of neutron-rich niobium isotopes in the mass region $A\ensuremath{\simeq}100$ has been investigated by $\ensuremath{\gamma}$-ray singles and $\ensuremath{\gamma}$-$\ensuremath{\gamma}$ coincidence measurements. The isotopes were produced by thermal-neutron induced fission of $^{235}\mathrm{U}$, $^{239}\mathrm{Pu}$, and $^{249}\mathrm{Cf}$, and niobium was separated from fission-product mixtures with an automated chemical procedure. Isomerism was found in the even-mass niobium isotopes with the following half-lives: 1.5 and 3.1 sec for $^{100}\mathrm{Nb}$, 1.3 and 4.3 sec for $^{102}\mathrm{Nb}$, and 0.8 and 4.8 sec for $^{104}\mathrm{Nb}$. Half-lives and $\ensuremath{\gamma}$ rays were assigned to the 15.0-sec $^{99}\mathrm{Nb}$, 7.1-sec $^{101}\mathrm{Nb}$, 1.5-sec $^{103}\mathrm{Nb}$, and \ensuremath{\sim}1-sec $^{106}\mathrm{Nb}$. Revised half-life values are given for the 7.1-sec $^{100}\mathrm{Zr}$ and 2.9-sec $^{102}\mathrm{Zr}$. RADIOACTIVITY $^{99,100,101,102,103,104,106}\mathrm{Nb}$, $^{100,102}\mathrm{Zr}$; measured ${T}_{\frac{1}{2}}$, ${E}_{\ensuremath{\gamma}}$, $\ensuremath{\gamma}$-$\ensuremath{\gamma}$-coin. $^{100,102,104}\mathrm{Mo}$ deduced levels. Fission $^{235}\mathrm{U}$, $^{239}\mathrm{Pu}$, $^{249}\mathrm{Cf}({n}_{\mathrm{th}},f)$; automated chemical separation procedure, Ge(Li) detectors.