Collectivity and Configuration Mixing inPb186,188andPo194

Abstract

Lifetimes of prolate intruder states in 186Pb and oblate intruder states in 194Po have been determined by employing, for the first time, the recoil-decay tagging technique in recoil distance Doppler-shift lifetime measurements. In addition, lifetime measurements of prolate states in 188Pb up to the 8+ state were carried out using the recoil-gating method. The B(E2) values have been deduced from which deformation parameters |beta2|=0.29(5) and |beta2|=0.17(3) for the prolate and the oblate bands, respectively, have been extracted. The results also shed new light on the mixing between different shapes.

Multi-quasiparticle excitation: Extending shape coexistence inA~190neutron-deficient nuclei

“…Recent experiments have confirmed the mixing scenario in 194 Po [14]. For 190 Po, low-lying band structure with prolate shape has been observed [37], which is also consistent with our calculation.…”

“…The mixing between different shapes is itself an interesting issue, although this may lead to considerable difficulty in isolating different shapes. One should notice that it is the shape mixing that complicates significantly the shape interpretations of the low-lying band structures in light polonium isotopes [3,14]. In practice, a two-or three-level-mixing analysis [15,16] or even a more sophisticated model [17,18] is needed to account for the shape mixing.…”

Configuration mixing in the neutron-deficientPb186−196isotopes

“…Starting from the schematic fit performed by Fossion et al [28], we slightly adjusted certain parameters [28]. were refined to describe the recently measured B(E2) values in 186,188 Pb [9] as well as possible. These B(E2) values provide a good tool to fix the mixing parameters because they are sensitive to the precise structure of the wave functions which in turn is sensitive to the mixing.…”

“…In 186,188 Pb, recent experiments [8,9,11] have provided extensive data on excitation spectra and the electromagnetic properties, rendering a thorough test for theoretical approaches. For the heavier 190−196 Pb isotopes, we compare the results of the calculations to the experimental level schemes.…”

“…The efforts of several research groups have made detailed experimental data such as energy spectra, electromagnetic decay properties and isotopic shifts available (see Refs. [7,8,9,10,11,12,13] for the most recent articles and Ref. [3] and references therein for a review article) .…”