Os-Pt区核的基态三轴形状

Triaxial Shape of Ground State in Os-Pt Region

在偶-偶核基态中寻找稳定的三轴形状,其中最大三轴形变为|γ|≈30°,仍然是核结构的一个主要主题。在本工作中,使用推转Woods-Saxon(WS)壳模型来研究Os-Pt区基态和集体转动态中可能的三轴形状。为寻找核态可能存在的三轴形变,具体用对力-形变-转动频率自洽推转壳模型对偶-偶^(176-202)Os和^(182-204)Pt同位素进行了总Routhian面计算。计算是在四极形变(β_(2),γ)网格中进行的,而十六极形变β_(4)可变。事实上,在四极形变(β_(2),γ)的每个网格点上,计算的能量相对于十六极形变β_(4)最小化。发现某些核的基态譬如^(196)Os和^(188-194)Pt既非扁椭球亦非长椭球,而是在这些核中基态极小值是形状非轴对称的,即三轴形变。同时,我们把从实验数据提取出的转动惯量与我们的计算结果作比较,显示实验数据不能很好地与转动假定相一致,说明有振动行为。此外,我们使用一种辅助的方法提取了平衡γ0值,该值支持我们的预言。

The search for stable triaxial shapes in the ground states of even-even nuclei,with a maximum triaxial deformation of|γ|≈30°,is still a major theme in nuclear structure.In the present work,we use the cranked Woods-Saxon(WS)shell mode to investigate possible triaxial shapes in ground and collective rotational states of Os-Pt region.Specifically,total-Routhiansurface calculations by means of the pairing-deformation-frequency self-consistent cranked shell model have been carried ou for even-even^(176-202)Os and^(182-204)Pt isotopes,in order to search for possible triaxial deformations of nuclear states.Calculations are performed in the lattice of quadrupole(β_(2),γ)deformations with the hexadecapoleβ_(4)variation.In fact,at each grid point of the quadrupole deformation(β_(2),γ)lattice,the calculated energy has been minimized with respect to the hexadecapole deformationβ_(4).It is found that some nuclear ground states such as in^(196)Os and^(188-194)Pt 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 equilibriumγ0 value,which support our predictions.