Radiations fromTb156

Abstract

The decay of Tb 166 has been studied following its production by the Tb 159 (Y,3w)Tb 156 reaction with 64-Mev bremsstrahlung. In the 5.6-day activity, 18 gamma transitions were detected with energies between 89 kev and 2060 kev. The K x-radiation of Gd was associated with this activity, while no Dy radiation was found. No annihilation radiation was detected. The gamma spectrum was observed in coincidence with the Gd x-ray and found to be closely similar to that observed alone. No evidence of /3-decay was found and it is concluded that the observed decay is by orbital electron capture. A relatively weak 5.5-hr activity, ascribable to Tb 156w , was also produced by the (y,3n) reaction.