Rotational structure of highly deformed 99Y: Decay of 99Sr

The level structure of the N = 60 isotone 99Y has been studied via the decay of 99Sr. γ singles and γ-γ coincidence measurements have resulted in 71 γ transitions placed in a decay scheme with 26 levels. γ-ray multiscaling measurements give a 99Sr half-life of 270 +- 10 ms. Five rotational bands, including the previously identified K = (5/2) ground-state band, have been identified in 99Y. Nilsson orbitals, with bandhead energies in keV in parentheses, associated with these five bands are (5/2)[422] (0), (5/2)[303] (487), (3/2)[301] (536), (1/2) [431] (1011), and (3/2)[431] (1119). The rotational features are consistent with an axially symmetric deformation in the range 0.3 to 0.4. The characteristics of these bands and their associated γ-ray transitions are discussed