Neutron-Deficient Activities of Praseodymium

Neutron-deficient radionuclides of praseodymium were produced by proton bombardment of enriched isotopes of cerium and neodymium. Two unreported activities were found, 22-min ${\mathrm{Pr}}^{135}$ and 70-min ${\mathrm{Pr}}^{136}$; the gamma and beta spectra of each were determined. Further study of 2.0-hr ${\mathrm{Pr}}^{138}$ and 4.5-hr ${\mathrm{Pr}}^{139}$ was also made, and gamma spectra of each are shown. The half-life of ${\mathrm{Pr}}^{137}$ is shown to be 1 year. Confirmation of assignment of 3.4-min ${\mathrm{Pr}}^{140}$ is made.