Artificially RadioactiveSe73andSe75

A radioactive isotope of 7.1-hour half-life has been produced by alpha-particle bombardment of germanium. Assignment of the isotope is made to ${\mathrm{Se}}^{73}$. Absorption measurements indicate the presence of a positron end point of 1.29 Mev. Aluminum x-ray absorption measurements indicate an x-ray emission with a mass absorption coefficient of 22.1 ${\mathrm{cm}}^2$/g, corresponding to 1.17A. Bombardment with alpha-particles of ${\mathrm{Ge}}^{70}$, enriched electromagnetically from 21.2 percent to 90 percent, further confirms the assignment of the activity to ${\mathrm{Se}}^{73}$. The half-life of ${\mathrm{Se}}^{75}$ is found to be 127±2 days over a decay period of 1000 days. In this activity $K$-capture and gamma-radiations of 0.22 Mev and 0.43 Mev are observed.