The structure and vibrational spectra of protonated Ar clusters Ar_nH⁺ (n = 2–3) are studied using potential energy surfaces at the CCSD(T)/aug-cc-pVTZ level and basis set. Ar binding energies, as well as position isomerism in Ar₃H⁺, were investigated. In our previous work, the spectra of Ar₂H⁺ reveal a strong progression of combination bands, which involves the asymmetric Ar–H⁺ stretch with multiple quanta of the symmetric Ar–H⁺ stretch. In this work, insights on the origin of such progression were examined using an adiabatic model. In addition, contributions from mechanical and electrical anharmonicity on the progressions’ intensities were also examined. Comparison of the calculated spectrum for the bare and Ar-tagged ions reveals that the reduction of the symmetry group, from D_∞h to either C_∞v or C_2v, results in a richer vibrational structure in the 500–1700 cm^–1 region. When compared with previously reported action spectra (D. C. McDonald III, D. T. Mauney, D. Leicht, J. H. Marks, J. A. Tan, J.-L. Kuo, and M. A. Duncan, J. Chem. Phys., 2016, 145, 231,101), it appears that the position isomers, because of the binding of the weakly bound Ar messenger, are needed to account for the additional bands in the infrared photodissociation spectrum for Ar₃H⁺. These findings demonstrate the active role of the messenger atom in relaxing some of the selection rules for the bare ion’s vibrational transitions – resulting in an augmentation of the bands in the action spectrum.

中文翻译：

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ArnH +的结构和振动光谱（n = 2-3）。

利用CCSD（T）/ aug-cc-pVTZ能级和基集上的势能面研究了质子化Ar团簇Ar _n H ⁺（n = 2–3）的结构和振动光谱。研究了Ar的结合能以及Ar ₃ H ^+中的位置异构现象。在我们先前的工作中，Ar ₂ H ⁺的光谱揭示了结合带的强进展，这涉及不对称的Ar–H ⁺伸展以及对称的Ar–H ^+的多个量子伸展。在这项工作中，使用绝热模型检查了关于这种进展的起源的见解。此外，还检查了机械和电气非谐对进度强度的贡献。对于裸露和Ar标记离子所计算的光谱的比较结果表明还原对称群的，从d _∞h要么ç _∞v或Ç _2V，导致了更丰富的振动结构在500-1700厘米^-1地区。与先前报道的作用谱（DC McDonald III，DT Mauney，D.Leicht，JH Marks，JA Tan，J.L.Kuo和MA Duncan，J.Chem.Phys。，2016，145，231,101）进行比较时，看来，由于弱结合的Ar信使的结合，需要位置异构体来说明Ar ₃ H ⁺的红外光解离光谱中的其他谱带。这些发现证明了信使原子在放松裸离子振动转变的某些选择规则方面的积极作用-导致了作用谱带的增加。