Decay studies of the new isotopesHf162,163

Abstract

The new isotopes $_{72}^{163}\mathrm{Hf}$ [${T}_{\frac{1}{2}}=40.0(6)$ s] and $_{72}^{162}\mathrm{Hf}$ [${T}_{\frac{1}{2}}=37.6(8)$ s] were produced in $_{60}^{142}\mathrm{Nd}$ ($_{12}^{24}\mathrm{Mg}$, $\mathrm{xn}$) reactions and transported to a measuring station by use of the He-jet technique. Decay properties were observed with $\ensuremath{\alpha}$, $\ensuremath{\gamma}$, and $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ spectroscopy. The $Z$ assignment of the new isotopes was based on a cross bombardment, $_{12}^{24}\mathrm{Mg}$+$_{59}^{141}\mathrm{Pr}$, and on results of $\ensuremath{\gamma}$-x-ray coincidence measurements. The mass assignment was deduced from measured excitation functions. Beta-delayed $\ensuremath{\gamma}$ rays were identified, 11 for $^{163}\mathrm{Hf}$ and 3 for $^{162}\mathrm{Hf}$, and level schemes for $_{71}^{163}\mathrm{Lu}$ and $_{71}^{162}\mathrm{Lu}$ are proposed based on the results of intensity and $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence measurements. A small $\ensuremath{\alpha}$ branch [${I}_{\ensuremath{\alpha}}={0.0087 }_{(\ensuremath{-}37}^{+17)}$%] with a decay energy of ${E}_{\ensuremath{\alpha}}=4308$ (10) keV was found in the decay of $^{162}\mathrm{Hf}$. The reduced $\ensuremath{\alpha}$ width ${W}_{\ensuremath{\alpha}}={2.6}_{(\ensuremath{-}1.2}^{+0.6)}$ for $^{162}\mathrm{Hf}$ is in accordance with those for neighboring nuclei. With the new $^{162}\mathrm{Hf}$ $\ensuremath{\alpha}$-decay energy, mass values were derived for $_{72}^{162}\mathrm{Hf}$, $_{74}^{166}\mathrm{W}$, $_{76}^{170}\mathrm{Os}$, $_{78}^{174}\mathrm{Pt}$, and $_{80}^{178}\mathrm{Hg}$. The new masses as well as values deduced for two-proton binding energies are compared with predictions of current mass formulas.RADIOACTIVITY $^{163,162}\mathrm{Hf}$ from $^{142}\mathrm{Nd}$($^{24}\mathrm{Mg}$,$\mathrm{xn}$); measured ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, ${E}_{\ensuremath{\alpha}}$, ${I}_{\ensuremath{\alpha}}$, and ${T}_{\frac{1}{2}}$; $^{163,162}\mathrm{Lu}$ deduced level schemes; deduced reduced $\ensuremath{\alpha}$ width for $^{162}\mathrm{Hf}$; deduced mass values for $^{162}\mathrm{Hf}$, $^{166}\mathrm{W}$, $^{170}\mathrm{Os}$, $^{174}\mathrm{Pt}$, and $^{178}\mathrm{Hg}$. He-jet technique; Ge(HP), Ge(Li), and Si surface-barrier detectors.