Radioactive isotopes of krypton resulting from fission of uranium have been separated in a mass-spectrograph. The half-lives and the relative fission yields of the isotopes ${\mathrm{Kr}}^{85}$, ${\mathrm{Kr}}^{87}$, and ${\mathrm{Kr}}^{88}$ have been measured. The maximum energies of the $\beta$-particles from ${\mathrm{Kr}}^{85}$ and ${\mathrm{Kr}}^{87}$ have been checked by absorption. It has been shown that ${\mathrm{Kr}}^{88}$ emits soft $\beta$-particles and an intense $\gamma$-radiation. This result combined with other measurements indicates that the $\beta$-spectrum of ${\mathrm{Kr}}^{88}$ is complex.

• Received 4 April 1949

DOI:https://doi.org/10.1103/PhysRev.76.279