engleski

Triaxiality in selenium-76

Background: Selenium and germanium nuclei are associated with both triaxiality and shape coexistence. The relative influence of these deformation effects on the low-lying nuclear structure remains the subject of much discussion with additional attention drawn to 76Se and 76Ge due to the potential for the observation of neutrinoless double-β decay. Purpose: Experimental observables related to the deformation of 76Se are lacking in precision. The purpose of the present paper is to provide electric quadrupole matrix elements with improved precision in order to determine the deformation of low-lying states in a model-independent manner. Methods: Sub-barrier Coulomb excitation was employed at the reaccelerated beam facility of the National Superconducting Cyclotron Laboratory using the JANUS setup. Using this method nineteen E2 matrix elements were extracted. Results: Extracted matrix elements agree within uncertainties with those in the literature but with improved precision. Through both a comparison with geometric models and a model-independent evaluation of E2 matrix elements using rotational invariants, the ground state of 76Se is best described as having a significant triaxial component, but is not maximally triaxially deformed. Conclusions: Selenium-76 exhibits a significant degree of triaxiality in its ground state. A detailed comparison with configuration-interaction calculations indicates that this can be well reproduced theoretically.

Spectroscopic factors, electromagnetic transitions

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