Triaxial Shape of Ground State in Os-Pt Region

The search for stable triaxial shapes in the ground states of even-even nuclei, with a maximum triaxial deformation of \left| \gamma \right| ≈30°, is still a major theme in nuclear structure. In the present work, we use the cranked Woods-Saxon(WS) shell model to investigate possible triaxial shapes in ground and collective rotational states of Os-Pt region. Specifically, total-Routhian-surface calculations by means of the pairing-deformation-frequency self-consistent cranked shell model have been carried out for even-even ^176-202Os and ^182-204Pt isotopes, in order to search for possible triaxial deformations of nuclear states. Calculations are performed in the lattice of quadrupole (\, \beta _2 , \gamma ) deformations with the hexadecapole \, \beta _4 variation. In fact, at each grid point of the quadrupole deformation (\, \beta _2 , \gamma ) lattice, the calculated energy has been minimized with respect to the hexadecapole deformation \, \beta _4 . It is found that some nuclear ground states such as in ¹⁹⁶Os and ^188-194Pt are neither oblate nor prolate. Instead, the ground states minima in these nuclei are axially asymmetric in shape, i.e., triaxial deformation. At the same time, we compare the experimentally deduced moments of inertia with our calculated results, which show that the experimental data do not agree well with the assumption of rotational motion. This indicates that they have vibrational behavior. In addition, a complementary approach is used to extract equilibrium \gamma _0 value, which support our predictions.