Abstract
The gamma and beta rays following the decay of I124 which was produced by Sb (α, n) reaction have been studied with scintillation spectrometers both single and in coincidence, and with a beta-ray spectrometer. Three gamma rays at 2.74–MeV, 2.29–MeV and 1.50–MeV and probably 0.9–MeV which were not found in decay of Sb124 were observed. The beta-gamma coincidence experiments revealed that the first positron group decays to the ground level of Te124 so that the energy difference between I124 and Te124 becomes 3.22–MeV, being consistent with beta decay energy systematics. In addition this beta component was found to have an unique 1st forbidden type spectrum, showing the spin and parity of the ground state of I124 is 2−. From these results we led to conclude the presence of two new levels at 2.88–MeV and 2.74–MeV which the spin value is probably 1 and the parity is negative. A doublet level at the second excited level previously reported was not confirmed in the present experiment. However a definite evidence of cross-over transition from the second level to the ground level was obtained which may indicate a presence of a 2+ level at the second excited level. The tentative decay scheme is proposed.
