OH同位素体$X^2Π$和$A^2Σ^+$态磁超精细结构的相对论耦合簇处理
A relativistic coupled-cluster treatment of magnetic hyperfine structure of the $X^2Π$ and $A^2Σ^+$ states of OH isotopologues
AI总结：
本研究采用相对论耦合簇方法精确计算OH同位素体X²Π和A²Σ⁺态的磁超精细结构常数，结果与实验高度一致，并扩展了核间距范围，为高振动能级研究奠定基础。
摘要：
对羟基自由基同位素体（$^{16,17}$OH(D)）在核间距范围$R \in [0.6, 1.8]$ Å内进行了磁偶极超精细结构（HFS）常数平行分量的从头计算。对于基电子态$X^2Π$，评估了由氧核和氢核共同诱导的HFS函数贡献。此外，还计算了激发态$A^2Σ^+$的氢诱导HFS曲线。该量子化学研究采用四分量相对论耦合簇（CC）方法，包括直到三重激发的贡献，即：三重簇振幅的贡献既通过微扰方式（CCSD(T)）研究，也通过完全迭代计算（CCSDT）研究。所得的氧诱导和氢诱导HFS函数代表了迄今为止最准确和可靠的理论预测，与从电子$X^2Π$态最低振动能级（$v\in [0,2]$）的高分辨率光谱数据推导出的半经验氢诱导HFS曲线表现出极好的一致性。对所有考虑的态，振动平均的从头计算值与实验值在1%以内一致。此外，HFS曲线定义的核间距范围已扩展到超过先前研究的范围，从而为在绝热和非绝热框架内对OH同位素体的更高转动振动能级进行准确HFS处理提供了坚实基础。
英文摘要：
$\textit{Ab initio}$ calculations of the parallel component of the magnetic dipole hyperfine structure (HFS) constant have been carried out for hydroxyl radical isotopologues ($^{16,17}$OH(D)) over the internuclear distance range $R \in [0.6, 1.8]$ Å. For the ground electronic state $X^2Π$, the HFS functions were evaluated for contributions induced by both oxygen and hydrogen nuclei. In addition, the hydrogen-induced HFS curve was calculated for the excited $A^2Σ^+$ state. The quantum-chemistry study employs a four-component relativistic coupled-cluster (CC) method, including excitations up to the triple level, namely: the contribution of triple-cluster amplitudes was studied both perturbatively (CCSD(T)) and through fully iterative calculations (CCSDT). The resulting oxygen- and hydrogen-induced HFS functions represent the most accurate and reliable theoretical predictions to date exhibiting excellent agreement with semiempirical curve for hydrogen-induced HFS derived from high-resolution spectroscopic data for the lowest vibrational levels ($v\in [0,2]$) of the electronic $X^2Π$ state. Vibrationally averaged $\textit{ab initio}$ values are consistent with experimental values within $1\%$ for all states considered. Furthermore, the internuclear distance range over which the HFS curves are defined has been extended beyond that of previous studies, thereby providing a robust foundation for accurate HFS treatments of higher-lying rovibrational levels of OH isotopologues within both adiabatic and non-adiabatic frameworks.
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