The infrared photodissociation spectra and the internal mobility of SF6, SiF4, and SiH4 dimers
The infrared photodissociation spectra and the internal mobility of SF6, SiF4, and SiH4 dimers
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SF6、SiF4 和 SiH4 二聚体的红外光解光谱和内部迁移率
DOI：
10.1063/1.457930
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发表时间：
1990
影响因子：
4.4
通讯作者：
A. Avoird
中科院分区：
文献类型：
--
作者：
J.W.I. van Bladel;A. Avoird
我们提出了一个分析的耦合源于不同的分子间相互作用（静电，交换，分散，感应）分裂和转移的频率的振动跃迁在货车范德华二聚体，并确定其强度。模型电位计算说明了（SF6）2，（SiF4）2和（SiH4）2的各种贡献的重要性和它们对单体取向的依赖性。结果，结合计算的平衡结构，障碍内旋转和（谐波）货车德瓦耳斯振动频率，导致几个观察这些配合物的红外光解光谱的解释是相关的。我们确认，在（SF6）2和（SiF4）2（取向无关）共振偶极偶极耦合占主导地位的外观的光谱。对于（SiH4）2，我们得出结论，但是，除了静电项是不可忽略的，而且，静电耦合导致取向依赖的振动频率和强度。这种取向依赖性与SiH4的v4模式中氢原子的大位移有关。我们还发现（SF_6）_2和（SiF_4）_2的内转动比（SiH_4）_2的内转动锁定得更强。特别是后者的齿轮内旋转可以很容易地发生在实验的分子束温度。
We present an analysis of the couplings originating from different intermolecular interactions (electrostatic, exchange, dispersion, induction) which split and shift the frequencies of the vibrational transitions in Van der Waals dimers, and determine their intensities. Model potential calculations illustrate the importance of the various contributions in (SF6)2, (SiF4)2 and (SiH4)2 and their dependence on the monomer orientations. The results, in conjunction with calculated equilibrium structures, barriers to internal rotation and (harmonic) Van der Waals vibrational frequencies, lead to several observations which are relevant for the interpretation of the infrared photodissociation spectra of these complexes. We confirm that in (SF6)2 and (SiF4)2 (orientation-independent) resonant dipole-dipole coupling dominates the appearance of the spectra. For (SiH4)2 we conclude, however, that other than electrostatic terms are not negligible and, moreover, that the electrostatic coupling leads to orientation-dependent vibrational frequencies and intensities. This orientational dependence is related to the large displacements of the hydrogen atoms in the v4 mode of SiH4. We also find that the internal rotations in (SF6)2 and (SiF4)2 are more strongly locked than those in (SiH4)2. Especially the geared internal rotations in the latter dimer could easily occur at the experimental molecular beam temperatures.