New neutron-rich isotopes of several rare-earth elements have been identified using on-line mass separation. The observed decay rates of K x rays in the mass separated fractions for which 153≤A≤162, together with the associated γ-decay spectra, provided direct isotopic identifications. New isotopes observed, with values of their half lives given in parentheses, are ${}_{}{}^{153}{}_{}{}^{}\mathrm{Pr}$ (4.3±0.2 s), ${}_{}{}^{155}{}_{}{}^{}\mathrm{Nd}$ (8.9±0.2 s), ${}_{}{}^{156}{}_{}{}^{}\mathrm{Nd}$ (5.47±0.11 s), ${}_{}{}^{157}{}_{}{}^{}\mathrm{Pm}$ (10.90±0.20 s), ${}_{}{}^{158}{}_{}{}^{}\mathrm{Pm}$ (4.8±0.5 s), and ${}_{}{}^{162}{}_{}{}^{}\mathrm{Eu}$ (10.6±1.0 s). In addition, we have confirmed recent reports of the observation of ${}_{}{}^{153}{}_{}{}^{}\mathrm{Nd}$ (28.9±0.4 s), ${}_{}{}^{154}{}_{}{}^{}\mathrm{Nd}$ (25.9±0.2 s), ${}_{}{}^{156}{}_{}{}^{}\mathrm{Pm}$ (26.70±0.10 s), ${}_{}{}^{159}{}_{}{}^{}\mathrm{Sm}$ (11.37±0.15 s), and ${}_{}{}^{160}{}_{}{}^{}\mathrm{Sm}$ (9.6±0.3 s). These half-life values are compared to the reuslts of theoretical predictions.

• Received 17 February 1987

DOI:https://doi.org/10.1103/PhysRevC.35.1965