Abstract
The near-yrast spectroscopy of 127Ba has been examined in detail up to spin 39 2 with the reaction 117Sn(13C, 3n) at 60 MeV incident energy. Gamma-ray spectroscopy was performed with the 8 π spectrometer, an instrument comprising 20 Compton-suppressed HPGe detectors and 71 BGO ball elements. Evidence is presented for the identification of single-neutron quasiparticle bands corresponding to Nilsson orbitals [532] 5 2, [523] 7 2, [411] 1 2 and [402] 5 2. The properties of the [523] 7 2 band suggest that the nucleus has a triaxial shape when that orbital is occupied. We draw attention to: (i) the signature splitting; (ii) staggering of B(E2) ratios; (iii) the mean Q1 Q2 ratio; and (iv) the comparison of the staggering in the B(M1) B(E2) ratios with the signature splitting. All these factors point to a γ-deformation in the neighbourhood of γ∼-20°. Based on the large B(M1) B(E2) ratios, the observed three-quasiparticle bands involve proton excitation. Of these bands, two have clear-cut structural assignments νh 11 2 π(h 11 2)2 and νd 5 2 π(h 11 2)2. However, the third band presented difficulties and no assignment was consistent with all the data. The shift in crossing frequency for the π(h 11 2)2 with a νh 11 2 spectator is very large and corresponds to a shift in the routhian of about 220 keV. This we interpret to be due to a negative γ-deformation for bands involving νh 11 2. The opposite shift of ∼300 keV for the same crossing with a νd 5 2 spectator cannot be explained as a shape polarization effect.
Original language | English |
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Pages (from-to) | 547-572 |
Number of pages | 26 |
Journal | Nuclear Physics A |
Volume | 539 |
Issue number | 3 |
DOIs | |
State | Published - Mar 30 1992 |
Externally published | Yes |
Keywords
- Nuclear reaction