同位旋标量对力对^(42)Ca中自旋-同位旋跃迁的影响  

Effects of isoscalar pairing force on spin-isospin transitions in ^(42)Ca

作　　者：郭亮 牛一斐[1,2] GUO Liang;NIU Yifei(School of Nuclear Science and Technology,Lanzhou University,Lanzhou 730000,China;Frontiers Science Center for Rare isotopes,Lanzhou University,Lanzhou 730000,China)

机构地区：[1]兰州大学核科学与技术学院,兰州730000 [2]兰州大学稀有同位素前沿科学中心,兰州730000

出　　处：《核技术》2023年第8期175-181,共7页Nuclear Techniques

基　　金：国家重点研发计划(No.2021YFA1601500);国家自然科学基金(No.12075104)资助。

摘　　要：本文利用相对论准粒子无规相位近似(Quasiparticle Random Phase Approximation,QRPA)模型研究了高斯型同位旋标量对力对原子核^(42)Ca中β−方向的伽莫夫-泰勒(Gamow-Teller,GT)和自旋-偶极(Spin-dipole,SD)跃迁的影响。结果表明:同位旋标量对力对于恢复SU(4)对称性从而重现实验上42Ca的低能量超级GT态至关重要。同位旋标量对力会使自旋反转的跃迁组分混合进入低能量GT态,从而增强低能量GT态的集体性,极大地增加其跃迁强度。同时,由于同位旋标量对力具有吸引性质,会减小低能量GT态的激发能。对于SD跃迁,同位旋标量对力对其激发能和跃迁强度的影响均不明显。[Background]Isoscalar pairing plays an important role in the spin-isospin excitation of nuclei.The discovery of super Gamow-Teller(GT)states in N≈Z nuclei has motivated researchers to explore the effects of isoscalar pairing on spin-isospin excitations.[Purpose]This study aims to investigate the effects of the isoscalar pairing interaction on GT and spin-dipole(SD)transitions in ^(42)Ca.[Methods]By solving the relativistic Hartree-Bogoliubov equation,we obtained the canonical single-nucleon basis and occupation amplitudes,which were used as inputs for the quasiparticle phase-random approximation(QRPA)calculation.Using the QRPA model,the GT and SD transitions in 42Ca were calculated,where the Gaussian isoscalar pairing force was adopted,with its strength being a free parameter.[Results]For GT states,the isoscalar pairing mixed the spin-flip transition configuration into the lowlying GT state,enhancing the collectivity of the low-energy GT state and significantly increasing its transition strength.Meanwhile,the isoscalar pairing force induced a shift of the low-energy GT state toward lower energies owing to the attractive properties of the isoscalar pairing force.For SD states,the isoscalar pairing force hardly affected the strengths and energies of SD states in ^(42)Ca.[Conclusions]Isoscalar pairing force was essential for restoring the SU(4)symmetry and hence reproducing the low-energy super GT state of ^(42)Ca in the experiment,whereas it hardly affected the SD states.

关 键 词：协变密度泛函理论 准粒子无规相位近似 同位旋标量对力 自旋-同位旋激发 

分 类 号：TL99[核科学技术—核技术及应用]