Decay ofPr137

A praseodymium isotope with a half-life of 75 min has been assigned to ${}_{}{}^{137}{}_{}{}^{}\mathrm{Pr}$. It decays with a $K$-capture-to-positron ratio of 2.5±0.2 and a maximum positron energy of 1.74±0.05 MeV. Approximately 6% of the disintegrations are to excited states of ${}_{}{}^{137}{}_{}{}^{}\mathrm{Ce}$. The energies and intensities of 28 gamma-ray transitions were measured with a Ge(Li) detector. Coincidences of the gamma rays were measured using two 3-in. NaI(T1) crystals and a multiparameter analyzer. An energy-level diagram consistent with the observed gamma-ray energies, intensities, and coincidences has been deduced.