Аннотация:Ab initio calculations of the parallel component of the magnetic dipole hyperfine structure (HFS)constant have been carried out for hydroxyl radical isotopologues (16,17OH(D)) over the internucleardistance range R ∈ [0.6, 1.8] Å. For the ground electronic state X2Π, the HFS functions wereevaluated for contributions induced by both oxygen and hydrogen nuclei. In addition, the hydrogen-induced HFS curve was calculated for the excited A2Σ+ state. The quantum-chemistry studyemploys a four-component relativistic coupled-cluster (CC) method, including excitations up to thetriple 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 dateexhibiting excellent agreement with semiempirical curve for hydrogen-induced HFS derived fromhigh-resolution spectroscopic data for the lowest vibrational levels (v ∈ [0, 2]) of the electronic X2Πstate. Vibrationally averaged ab initio values are consistent with experimental values within 1% forall states considered. Furthermore, the internuclear distance range over which the HFS curves aredefined has been extended beyond that of previous studies, thereby providing a robust foundationfor accurate HFS treatments of higher-lying rovibrational levels of OH isotopologues within bothadiabatic and non-adiabatic frameworks.
