Prolate shape of 140Ba from a first combined Doppler-shift and Coulomb-excitation measurement at the REX-ISOLDE facility

Background: Quadrupole moments of excited nuclear states are important observables for geometrically interpreting nuclear structure in terms of deformed shapes, although data are scarce and sometimes ambiguous, in particular, in neutron-rich nuclides.

Purpose: A measurement was performed for determining the spectroscopic quadrupole moment of the 2+
1 state of 140Ba in order to clarify the character of quadrupole deformation (prolate or oblate) of the state in its yrast sequence of levels.

Method: We have utilized a new combined technique of lifetime measurement at REX-ISOLDE and MINIBALL using the Doppler-shift attenuation method (DSAM) and a reorientation analysis of Coulomb-excitation yields.

Results: On the basis of the new lifetime of 𝜏⁡(2+
1)=10.4+2.2
−0.8 ps the electric quadrupole moment was determined to be 𝑄⁡(2+
1)=−0.52⁢(34) 𝑒b, indicating a predominant prolate deformation.

Conclusions: This finding is in agreement with beyond-mean-field calculations using the Gogny D1S force and with results from the Monte Carlo shell-model approach.

Authors: C. Bauer, T. Behrens, V. Bildstein, A. Blazhev, B. Bruyneel, J. Butterworth, E. Clément, L. Coquard, J.L. Egido, A. Ekström, C.R. Fitzpatrick, C. Fransen, R. Gernhäuser, D. Habs, H. Hess, J. Leske, T. Kröll, R. Krücken, R. Lutter, P. Marley, T. Möller, T. Otsuka, N. Patronis, A. Petts, N. Pietralla, T.R. Rodriguez, N. Shimizu, C. Stahl, I. Stefanescu, T. Stora, P.G. Thirolf, D. Voulot, J. van de Walle, N. Warr, F. Wenander, A. Wiens

Doi: 10.1103/PhysRevC.86.034310

Issue number:

Journal: Phys. Rev. C

Page number: 034310

Published on: 2012-09-07

Year: