Neutron-hole states in 131Sn and spin-orbit splitting in neutron-rich nuclei
Neutron-hole states in 131Sn and spin-orbit splitting in neutron-rich nuclei
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DOI：
10.1016/j.physletb.2018.08.005
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发表时间：
2018-10
影响因子：
4.4
通讯作者：
R. Orlandi;S. Pain;S. Ahn;A. Jungclaus;K. Schmitt;D. Bardayan;W. Catford;R. Chapman;K. Chipps;J. Cizewski;C. G. Gross;M. Howard;K. L. Jones;R. Kozub;B. Manning;M. Matoš;K. Nishio;P. D. Malley;W. Peters;S. T. Pittman;A. Ratkiewicz;C. Shand;J. Smith;M. Smith;T. Fukui;J. Tostevin;Y. Utsuno
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文献类型：
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作者：
R. Orlandi;S. Pain;S. Ahn;A. Jungclaus;K. Schmitt;D. Bardayan;W. Catford;R. Chapman;K. Chipps;J. Cizewski;C. G. Gross;M. Howard;K. L. Jones;R. Kozub;B. Manning;M. Matoš;K. Nishio;P. D. Malley;W. Peters;S. T. Pittman;A. Ratkiewicz;C. Shand;J. Smith;M. Smith;T. Fukui;J. Tostevin;Y. Utsuno
在原子核中，自旋-轨道相互作用源于核子的轨道运动与其本征自旋的耦合。最近的实验和理论工作表明，丰中子核中的自旋-轨道相互作用减弱，远不稳定。为了研究这一现象，我们研究了132Sn单空穴和单粒子价中子轨道的自旋轨道能分裂。在橡树岭国家实验室的霍利菲尔德放射性离子束装置上对132Sn(d，t)131Sn反应进行了逆运动学研究，根据测量的三子微分截面确定了131Sn中单空穴态的光谱强度。最低的3/2+、1/2+和5/2+态的光谱因子与它们的最大值(2j+1)相一致，证实了在132Sn处N=82的强壳层闭合。我们比较了131Sn单空穴态和133Sn单粒子态的自旋轨道分裂，这些分裂是在最近对132Sn(d，p)133Sn反应的测量中测得的。我们发现弱束缚的3p轨道的能量分裂比束缚良好的2d轨道的能量分裂要小得多，并且所有观测到的能量分裂都可以通过使用一体自旋-轨道相互作用和标准半径和扩散的Wood-Saxon势进行计算而得到很好的再现。观察到的自旋-轨道分裂的减少可以用弱束缚轨道的扩展径向波函数来解释，而不会引起自旋-轨道强度的减弱。
In atomic nuclei, the spin-orbit interaction originates from the coupling of the orbital motion of a nucleon with its intrinsic spin. Recent experimental and theoretical works have suggested a weakening of the spin-orbit interaction in neutron-rich nuclei far from stability. To study this phenomenon, we have investigated the spin-orbit energy splittings of single-hole and single-particle valence neutron orbits of 132 Sn. The spectroscopic strength of single-hole states in 131 Sn was determined from the measured differential cross sections of the tritons from the neutron-removing 132 Sn (d, t) 131 Sn reaction, which was studied in inverse kinematics at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The spectroscopic factors of the lowest 3/2+, 1/2+ and 5/2+ states were found to be consistent with their maximal values of (2 j+ 1), confirming the robust N= 82 shell closure at 132 Sn. We compared the spin-orbit splitting of neutron single-hole states in 131 Sn to those of single-particle states in 133 Sn determined in a recent measurement of the 132 Sn (d, p) 133 Sn reaction. We found a significant reduction of the energy splitting of the weakly bound 3p orbits compared to the well-bound 2d orbits, and that all the observed energy splittings can be reproduced remarkably well by calculations using a one-body spin-orbit interaction and a Woods–Saxon potential of standard radius and diffuseness. The observed reduction of spin-orbit splitting can be explained by the extended radial wavefunctions of the weakly bound orbits, without invoking a weakening of the spin-orbit strength.