THE DISINTEGRATION OF Tm170

Abstract

The radiations from the decay of Tm170 (127 day) have been studied by means of a lens type β-ray spectrometer, a scintillation spectrometer, short resolving time (2τ0 = 2 × 10−9 sec.) coincidence counting techniques, and a pair of lens type β-ray spectrometers placed end to end with coincidence counting of the focused radiations from a single source. A disintegration scheme is proposed which is consistent with the experimental results. Decay is found to be by negative β-ray emission; the spectrum consists of two components, one of maximum energy 968 ± 4 kev. (76%) proceeding to the ground state of Yb170 and one of maximum energy 884 ± 4 kev. (24%) to an excited state in Yb170 followed by emission of a γ ray or conversion electron to the ground state. The γ-ray transition in Yb170 is found to have an energy of 84.1 ± 0.1 kev., a half-life of (1.57 ± 0.05) × 10−9 sec, and conversion coefficients aK = 1.60 ± 0.15, aL = 4.1 ± 0.5, aM = 1.2 ± 0.2 which show that it is electric quadrupole in character. Upper limits are given for decay by K capture, 0.3%, or positive β-ray emission, 0.01%, and also for the occurrence of other γ rays.