Spectroscopy of 123I.

The level scheme of [sup 123]I has been studied by in-beam gamma-ray spectroscopy in the fusion evaporation reaction [sup 121]Sb([alpha],2[ital n][gamma])[sup 123]I. Gamma-gamma coincidences and gamma-ray angular distributions have been measured with large-volume high-resolution germanium detectors. The multipolarities and multipole mixing ratios have been determined for some of the transitions. Several new levels and transitions are observed and assigned to [sup 123]I. A revised decay scheme is presented showing new levels and transitions associated with various bands in [sup 123]I. The band structure of [sup 123]I is discussed and interpreted in the light of theoretical predictions and evidence is presented for possible coexistence of different shapes in this nucleus.