Decay ofSm156

The radiations following the decay of 9.4±0.2 h ${\mathrm{Sm}}^{156}$ have been studied using techniques of scintillation spectrometry and $4\pi$ beta counting. The isotope was produced by fissioning natural uranium in a high neutron flux and except for ${\mathrm{Sm}}^{153}$, was separated from other fission products by radiochemical techniques. The following gamma-ray energies were observed in the decay of ${\mathrm{Sm}}^{156}$: 38 keV, x rays (∼20%), 87 keV (40%), 165 keV (18%), 203 keV (29%), 252 keV (5%), and 290 keV (3%). The 87-keV gamma transition was found to be coincident with both the 165- and 203-keV gamma transitions. Its $K$-shell conversion coefficient is 0.35±0.02. Angular correlation studies indicated the 87-203 keV gamma anisotropy to be about -0.25 and the 87-165 keV gamma anisotropy to be $0<A<\mathrm{}0.1\mathrm{}$. Fermi plots of the beta spectra coincident with the 165- and 203-keV gamma rays produced identical end points of 430±10 keV. Another beta group, 45% in abundance, had an end point of 715±15 keV and presumably goes to the ground state of ${\mathrm{Eu}}^{156}$.