Large-scale shell-model calculations for unnatural-parity high-spin states in neutron-rich Cr and Fe isotopes
Large-scale shell-model calculations for unnatural-parity high-spin states in neutron-rich Cr and Fe isotopes
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DOI：
10.1103/physrevc.91.024320
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发表时间：
2014-11
影响因子：
3.1
通讯作者：
T. Togashi;N. Shimizu;Y. Utsuno;T. Otsuka;M. Honma
中科院分区：
文献类型：
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作者：
T. Togashi;N. Shimizu;Y. Utsuno;T. Otsuka;M. Honma
我们用大规模壳模型计算研究了富中子铬和铁同位素中的非自然宇称高自旋态。这些壳层模型计算是在$FP\Text{-Shell}+0{g}_{9/2}+1{d}_{5/2}$轨道的模型空间内进行的，截断允许$1\保证数学{\hbar}\\确保数学{\omega}$激发中子。有效哈密顿量由$FP$壳层轨道的GXPF1BR和${V}_{\mathm{MU}}$组成，其他部分作了修改。本文的壳层模型计算可以描述和预测铬和铁同位素中自然的和非自然的宇宙态直到高自旋态的能级。总能面总体上呈现拉长形变，表明一个中子激发到0{g}{9/2}$轨道上起到了促进拉长形变的作用。对于奇质量铬和铁同位素中的正(非自然)宇称态，它们的能级和拉长形变表明了粒子+转子模型的去耦合极限。奇质量铬、铁和镍同位素的9/{2}{1}^{+}$能级从$N=29$急剧下降到$N=35$，其原因是费米面接近数学轨道0{g}{9/2}$。
We investigate unnatural-parity high-spin states in neutron-rich Cr and Fe isotopes using large-scale shell-model calculations. These shell-model calculations are carried out within the model space of $fp\text{-shell}+0{g}_{9/2}+1{d}_{5/2}$ orbits with the truncation allowing $1\ensuremath{\hbar}\ensuremath{\omega}$ excitation of a neutron. The effective Hamiltonian consists of GXPF1Br for $fp$-shell orbits and ${V}_{\mathrm{MU}}$ with a modification for the other parts. The present shell-model calculations can describe and predict the energy levels of both natural- and unnatural-parity states up to the high-spin states in Cr and Fe isotopes with $N\ensuremath{\le}35$. The total energy surfaces present prolate deformations on the whole and indicate that the excitation of one neutron into the $0{g}_{9/2}$ orbit plays the role of enhancing prolate deformation. For positive (unnatural)-parity states in odd-mass Cr and Fe isotopes, their energy levels and prolate deformations indicate the decoupling limit of the particle-plus-rotor model. The sharp drop of the $9/{2}_{1}^{+}$ levels in going from $N=29$ to $N=35$ in odd-mass Cr, Fe, and Ni isotopes is explained by the Fermi surface approaching the $\ensuremath{\nu}0{g}_{9/2}$ orbit.