Search for two-quantum decay of In114m

Abstract

The 192 keV isomeric state in In114 decays with a half-life of 50 d. Measurements of the K/L ratio with a double focusing spectrometer confirmed that the transition to the ground state is of E4 character. The level might alternatively decay by two-quantum emission, which should be particularly probable in this case, since it may proceed by enhanced E2 transitions. Considering that the 192 keV E4 transition is strongly retarded, the In114m case seems to be especially suitable for detection of two-quantum decay. This mode of decay was experimentally investigated by coincidence measurements between gamma rays of 96 keV and other gamma-rays, displayed on a multichannel analyser. The result shows that the relative probability for two-quantum decay is less than 3 · 10−5, a value which is orders of magnitude lower than theoretical estimates. Analogous experiments with conversion electrons might prove valuable.