We express our gratitude to the RIKEN Nishina Center accelerator staff for providing the stable and high-intensity uranium beam and to the BigRIPS team for operating the secondary beams. The development of MINOS and the core MINOS team were supported by the European Research Council through the ERC Grant No. MINOS-258567. This work was supported by the IPA program at RIKEN Nishina Center, by GSI-Darmstadt computing facilities and Ministerio de Economía y Competitividad under Contract FIS-2014- 53434 and Programa Ramón y Cajal 2012 No. 11420, by the GermanBMBFGrantsNo. 05P15PKFNA, No. 05P12RDFN8, and No. 05P15RDFN1, by Ministerio de Economy Competitividad under Contract FPA2014-57196-C5-4-P, by the Hundred-Talent Program at Chinese Academy of Sciences, by the National Natural Science Foundation of China under Grant No. 11405224, by the Japan Society for the Promotion of Science under Grant No. 2604327, and by the Vietnam Ministry of Science and Technology.

Neutron-rich Se88,90,92,94 isotopes were studied via in-beam γ-ray spectroscopy after nucleon removal reactions at intermediate energies at the Radioactive Isotope Beam Factory. Based on γ-γ coincidence analysis, low-lying excitation level schemes are proposed for these nuclei, including the 21+, 41+ states and 22+ states at remarkably low energies. The low-lying 22+ states, along with other features, indicate triaxiality in these nuclei. The experimental results are in good overall agreement with self-consistent beyond-mean-field calculations based on the Gogny D1S interaction, which suggests both triaxial degree of freedom and shape coexistence playing important roles in the description of intrinsic deformations in neutron-rich Se isotopes.

S. Chen et al. -- 6 pags., 4 figs.

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