Department of Mathematical Physics

Ingemar Ragnarsson

Single particle excitations and properties of multipole band terminations near spin 50 hbar in 158Er.

J. Simpson, M.A. Riley, S.J. Gale, J.F. Sharpey-Schafer, .........., T. Bengtsson and I. Ragnarsson

Abstract: The competion between collective rotation and single-particle behaviour at high spin in 158Er has been investigated with the Eurogam Spectrometer. Band terminating states have been observed in three structures at I = 46+,. 48- and 49- and specific single-particle configurations are assigned by comparison with cranked Nilsson-Strutinsky calculations. These special states are found to be related by very simple single-particle excitations. These data indicate that an oblate mean field (eps ~ -0.14) is established for a nuclear core plus 12 aligned valence nucleons which is stable against single-particle rearrangements. In the (pi, alpha) = (+,0) states the collective and weakly oblate collective terminating structures are observed to coexist between 30+ and 46+.