High-spin structures in 137Sm: Role of the beta -driving nu i13/2 intruder in deformation enhancement.

Abstract

Collective band structures have been observed in the neutron-deficient /sup 137/Sm nucleus by means of the /sup 104/Pd(/sup 37/Cl,/ital p/3/ital n/..gamma..) reaction. At lowspins, the yrast band, built on the ..nu../ital h//sub 11/2/(514)9/2/sup /minus// Nilsson orbital, exhibits a large signaturesplitting (/similar to/100 keV) consistent with a significant triaxial shape(..gamma../similar to//minus/20/degree/). At higher spins, two sidebands were observed whichare characterized by strong ..delta../ital I/=1 transitions and a lack ofsignature splitting. These band structures contain rotationally alignedlower-midshell /ital h//sub 11/2/ protons which drive the nucleustowards the prolate (..gamma..=0/degree/) shape. In addition, a decoupled bandwas observed built on an /ital I//sup ..pi../= (17/2/sup +/)state. This band reveals a 50% increase in the dynamic moment of inertiaconsistent with an enhanced quadrupole deformation (..beta../similar to/0.35),and is believed to be built on the ..beta..-driving..nu../ital i//sub 13/2/ (660)1/2/sup +/single-quasiparticle state, intruding from two harmonic oscillator shellsabove. The ..beta..-driving properties of this orbital represent an importantmechanism in the evolution of enhanced nuclear deformation in this region. Theresults are compared to those of the /ital N/=75 /sup 133/Ce,/sup 135/Nd, and /sup 139/Gd isotones.