Electric dipole transitions in the relativistic quasiparticle random-phase approximation at finite temperature
Electric dipole transitions in the relativistic quasiparticle random-phase approximation at finite temperature
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DOI：
10.1103/physrevc.109.014314
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发表时间：
2023-10
影响因子：
3.1
通讯作者：
Amandeep Kaur;E. Yüksel;Nils Paar
中科院分区：
文献类型：
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作者：
Amandeep Kaur;E. Yüksel;Nils Paar
在高温恒星环境中，有限的温度会对核结构的性质和与核过程相关的激发产生不同的影响。本文采用基于相对论能量密度泛函和点耦合相互作用的自洽有限温度相对论准粒子随机位相近似(FT-RQRPA)来描述电偶极跃迁中的温度效应。通过考虑热效应和配对效应，我们研究了温度范围为$T=$0-2 MeV的闭壳核和开壳核的E_1激发，范围从{40}~(60)~(100)~(140)。在考虑的温度范围内，向量巨偶极子共振强度略有修改，而在高温下，12 MeV的中子核出现了新的低能峰，其强度不可忽略。对相关两准粒子组态的分析揭示了在有限温度下，由于态的热解阻，新的激发通道是如何打开的。研究还考察了电偶极子极化率的同位旋和温度关系，结果表明，随着温度的升高，电偶极子极化率的值有系统地增加，在丰中子核中观察到的影响更为明显。本文介绍的FT-RQRPA将为核反应研究中有限温度下的γ射线强度函数的微观计算开辟新的前景。
Finite temperature results in various effects on the properties of nuclear structure and excitations of relevance for nuclear processes in hot stellar environments. Here we introduce the self-consistent finite temperature relativistic quasiparticle random phase approximation (FT-RQRPA) based on relativistic energy density functional with point coupling interaction for describing the temperature effects in electric dipole (E1) transitions. We perform a study of E1 excitations in the temperature range $T=$ 0-2 MeV for the selected closed- and open-shell nuclei ranging from $^{40}$Ca to $^{60}$Ca and $^{100}$Sn to $^{140}$Sn by including both thermal and pairing effects. The isovector giant dipole resonance strength is slightly modified for the considered range of temperature, while new low-energy peaks emerge for $E<$12 MeV with non-negligible strength in neutron-rich nuclei at high temperatures. The analysis of relevant two-quasiparticle configurations discloses how new excitation channels open due to thermal unblocking of states at finite temperature. The study also examines the isospin and temperature dependence of electric dipole polarizability ($\alpha_D$), resulting in systematic increase in the values of $\alpha_D$ with increasing temperature, with a more pronounced effect observed in neutron-rich nuclei. The FT-RQRPA introduced in this work will open perspectives for microscopic calculation of $\gamma$-ray strength functions at finite temperatures relevant for nuclear reaction studies.