Decay of 66-MinIn11049

A source of pure 66-min ${\mathrm{In}}^{110}$, particularly free from 4.9-h ${\mathrm{In}}^{110m}$, has been made by bombarding a natural indium foil with about 100-MeV protons, and chemically separating tin (predominantly ${\mathrm{Sn}}^{110}$, which is the parent of only 66-min ${\mathrm{In}}^{110}$) from the indium target. Scintillation spectrometer studies have shown that the well known 280-keV gamma ray is emitted in the decay of 4-h ${\mathrm{Sn}}^{110}$ to 66-min ${\mathrm{In}}^{110}$, and the following gamma rays are emitted in the decay of 66-min ${\mathrm{In}}^{110}$: 656, 820, 1120, 1400, 1630, 1780, 2130, 2300, 2400, 2600, 2750, 3000, 3400, and 3650 KeV. The following levels in ${\mathrm{Cd}}^{110}$, fed from the decay of 66-min ${\mathrm{In}}^{110}$, are postulated: 656, 1474, 1541, 1790, 1910, 2060, 2820, 3110, 3400, and 3650 keV. From the study of gamma rays in simultaneous coincidence with two annihilation quanta, the intensity of the positron branching to the 656-, 1474-, and 1790-keV states are estimated to be 71, 0.2, and 0.1%, respectively. The $log\mathrm{ft}$ to these states are calculated to be 5.5, 7.4, and 7, respectively. It is concluded that the allowed positron decay to the 1474-keV state is retarded by a factor of about 100.