New Erbium Isotope,Er155

A new erbium isotope ${}_{}{}^{155}{}_{}{}^{}\mathrm{Er}$ was produced by bombarding enriched ${}_{}{}^{156}{}_{}{}^{}\mathrm{Dy}$ with $\alpha$ particles accelerated in the Oak Ridge Isochronous Cyclotron. In the experiments, recoil nuclei ejected from the thin target were collected on beryllium foils. After bombardment, the activity collected on the catchers was assayed with an $\alpha$-particle Si(Au) spectrometer. The new isotope was found to have a half-life of 5.3±0.3 min; its $\alpha$-decay energy was measured to be 4.01±0.03 MeV. The mass assignment of ${}_{}{}^{155}{}_{}{}^{}\mathrm{Er}$ was established by measuring an excitation function for its production for $\alpha$-particle bombarding energies from 59.2 to 72.6 MeV.