Radiations fromSelenium75

The radiations from 125-day ${\mathrm{Se}}^{75}$ have been examined by means of a thin lens spectrometer and absorption-coincidence techniques. ${\mathrm{Se}}^{75}$ was found to decay to ${\mathrm{As}}^{75}$ by orbital electron capture. The energies of ten transitions (${0.066}_6$, ${0.076}_6$, ${0.098}_3$, ${0.124}_1$, ${0.138}_4$, ${0.203}_2$, ${0.268}_8$, ${0.281}_4$, ${0.307}_8$, and ${0.405}_0$ Mev) were observed in the photoelectron and internal conversion spectra determined with the spectrometer. A decay scheme is proposed on the basis of the absorption-coincidence and spectrometer data. The multipole order of the 98.3-kev transition is discussed.