P. Vymers

Dipole Bands in 196Hg

High spin states in 196Hg have been populated in the 198Pt(α,6n) reaction at 65 MeV and the level scheme has been extended. A new dipole band has been observed and a previously observed dipole has been confirmed. Excitation energies, spins and parities of these bands were determined from DCO ratio and linear polarization measurements. Possible quasiparticle excitations responsible for these structures are discussed.

Possible chiral bands in 194Tl

High spin states in 194Tl, excited through the 181Ta(18O,5n) fusion evaporation reaction, were studied using the AFRODITE array at iThemba LABS. Candidate chiral bands built on the πh9/2⊗νi13/21 configuration were found. Furthermore these bands were observed through a band crossing caused by the excitation of a νi13/2 pair. Above the band crossing the excitation energies remain close, suggesting that chirality may persist for the four quasiparticle configuration too.

Shape Transitional Nuclei: What can we learn from the Yrare States? or Hello the Double Vacuum; Goodbye β‐vibrations!

The results of our measurements on the yrare states up to spin 20ℏ in 152,154,155Gd, using (α,xn) reactions and the AFRODITE γ‐ray spectrometer, are presented. We find that in 155Gd the decay scheme is divided into levels feeding the [505]11/2− band, that is extruded by the prolate deformation from the h11/2 orbital, and levels feeding the i13/2[651]3/2+ intruder orbital and the h9/2[521]3/2− orbital. The decay scheme of 154Gd is very complex. We find no evidence for the existence of β‐vibrational levels below 1.5 MeV. We discover that the level scheme can be best understood as a set of collective states built on the ground state configuration |01+> plus a “congruent” set of collective states based on the |02+> state at 681 keV. The data suggest that this second vacuum has reduced pairing. Our data do not support IBA and phonon interpretations of these transitional nuclei.