Decay ofNd15160(12 min)

The decay of ${\mathrm{Nd}}^{151}$(12 min) is characterized by beta emission to excited states in ${\mathrm{Pm}}^{151}$. This activity has been investigated by means of the Argonne 256-channel scintillation coincidence spectrometer and photographic internal-conversion-electron spectrographs. Sources were prepared by neutron irradiation of neodymium oxide, enriched in ${\mathrm{Nd}}^{150}$, in the Argonne reactor CP-5. The presence of six beta-ray branches is deduced; four of these were observed experimentally by means of absorption methods. Thirty gamma transitions are reported. Twenty-seven of these and the six beta-ray groups are fitted into a decay scheme which indicates the presence of excited states in ${\mathrm{Pm}}^{151}$ at 0.1172, 0.2560, 0.4265, 0.5336, 0.852, 0.937, 1.12, 1.29, 1.63, 1.87, and 2.17 Mev. The total energy difference between the ${\mathrm{Nd}}^{151}$ parent and the ${\mathrm{Pm}}^{151}$ ground state is found to be (2.4±0.1) Mev. The low-lying levels in ${\mathrm{Pm}}^{151}$ are discussed with particular reference to the possible existence of a rotational series based on the ground state.