Neutron deficient isotopes of rubidium have been prepared from bromine by bombardment with helium ions in the Berkeley 184-inch and 60-inch cyclotrons. The properties of these isotopes are as follows:

The mass numbers were determined with a mass spectrograph. ${\mathrm{Rb}}^{81}$ has been shown to decay to the 13-sec. krypton, thereby assigning it to ${\mathrm{Kr}}^{81}$. Electrons from the conversion of a 190-kev gamma-ray caused by this krypton are observed with the ${\mathrm{Rb}}^{81}$ radiations.

• Received 10 July 1950

DOI:https://doi.org/10.1103/PhysRev.80.646