Shape coexistence in the neutron-deficient even-even 182−188Hg isotopes studied via Coulomb excitation

Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85 MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in 182−188Hg were extracted. Information on the deformation of the ground and the first excited 0+ states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0+ state was noted in 182,184Hg. The results are compared to beyond mean field and interacting-boson based models and interpreted within a two-state mixing model. Partial agreement with the model calculations was obtained. The presence of two different structures in the light even-mass mercury isotopes that coexist at low excitation energy is firmly established.The authors would like to thank the ISOLDE facility for providing excellent beams. This work was supported by the FWO-Vlaanderen (Belgium), an FWO Pegasus Marie Curie Fellowship (L. P. G.), by GOA/2010/010 (BOF KULeuven), by the IAP Belgian Science Policy (BriX network P6/23 and P7/12), by the European Commission within the 7th Framework Programme through I3-ENSAR (Contract No. RII3-CT-2010-262010), by the U. K. Science and Technology Facilities Council, by the German BMBF under Contracts No. 06DA9036I, No. 05P12RDCIA, No. 06KY205I, No. 05P09PKCI5, No. 05P12PKFNE, No. 05P12WOFNF, and No. 09MT9156, Academy of Finland (Contract No. 131665), by the Spanish MINECO through FPA2010-17142 project and the Spanish Project No. FIS2011-28738-C02-02