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

Phys. Rev. C

86
034310
(2012)
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

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.

DOI
10.1103/PhysRevC.86.034310
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