New Isotopes:Er172andTm172

Two new isotopes, ${\mathrm{Er}}^{172}$ of half-life 49.8±1 hr, and ${\mathrm{Tm}}^{172}$ of half-life 63.6±0.3 hr, have been found. The mass assignment of ${\mathrm{Tm}}^{172}$ was proven by direct mass separation, and that of ${\mathrm{Er}}^{172}$ by genetic relationship. The ${\mathrm{Tm}}^{172}$ isotope was found to emit a 1.5-Mev ${\beta }^{-}$ particle, $\gamma$ rays of 1.79, 1.44, 1.09, 0.40, 0.18, and 0.076 Mev, and a $K$ x-ray of 0.049 Mev. The mass assignments of ${\mathrm{Er}}^{165}$, ${\mathrm{Er}}^{171}$, and ${\mathrm{Tm}}^{171}$ were verified.