Diborane anharmonic vibrational frequencies and Intensities: Experiment and theory

IF 1.4 4区 物理与天体物理 Q4 PHYSICS, ATOMIC, MOLECULAR & CHEMICAL
Aaron I. Strom , Ibrahim Muddasser , Guntram Rauhut , David T. Anderson
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引用次数: 0

Abstract

The vibrational dynamics of diborane have been extensively studied both theoretically and experimentally ever since the bridge structure of diborane was established in the 1950s. Numerous infrared and several Raman spectroscopic studies have followed in the ensuing years at ever increasing levels of spectral resolution. In parallel, ab initio computations of the underlying potential energy surface have progressed as well as the methods to calculate the anharmonic vibration dynamics beyond the double harmonic approximation. Nevertheless, even 70 years after the bridge structure of diborane was established, there are still significant discrepancies between experiment and theory for the fundamental vibrational frequencies of diborane. In this work we use parahydrogen (pH2) matrix isolation infrared spectroscopy to characterize six fundamental vibrations of B2H6 and B2D6 and compare them with results from configuration-selective vibrational configuration interaction theory. The calculated frequencies and intensities are in very good agreement with the pH2 matrix isolation spectra, even several combination bands are well reproduced. We believe that the reason discrepancies have existed for so long is related to the large amount of anharmonicity that is associated with the bridge BH stretching modes. However, the calculated frequencies and intensities reported here for the vibrational modes of all three boron isotopologues of B2H6 and B2D6 are within ± 2.00 cm−1 and ± 1.44 cm−1, respectively, of the experimental frequencies and therefore a refined vibrational assignment of diborane has been achieved.

Abstract Image

二硼烷非谐振动频率和强度:实验与理论
自 20 世纪 50 年代确定二硼烷的桥式结构以来,人们对其振动动力学进行了广泛的理论和实验研究。在随后的几年里,人们又以越来越高的光谱分辨率进行了大量的红外光谱研究和一些拉曼光谱研究。与此同时,底层势能面的非初始计算以及双谐波近似之外的非谐波振动动力学计算方法也取得了进展。然而,即使在二硼烷的桥式结构确定 70 年后,实验与理论在二硼烷的基本振动频率方面仍存在显著差异。在这项工作中,我们使用对氢 (pH2) 基质隔离红外光谱法表征了 B2H6 和 B2D6 的六次基振,并将其与构型选择性振动构型相互作用理论的结果进行了比较。计算出的频率和强度与 pH2 基质分离光谱非常吻合,甚至几个组合带也得到了很好的再现。我们认为,长期存在差异的原因与桥 BH 拉伸模式的大量非谐波有关。不过,本文报告的 B2H6 和 B2D6 所有三种硼同素异形体的振动模式的计算频率和强度分别在实验频率的 ± 2.00 cm-1 和 ± 1.44 cm-1 范围内,因此二硼烷的振动赋值已经得到完善。
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来源期刊
CiteScore
2.70
自引率
21.40%
发文量
94
审稿时长
29 days
期刊介绍: The Journal of Molecular Spectroscopy presents experimental and theoretical articles on all subjects relevant to molecular spectroscopy and its modern applications. An international medium for the publication of some of the most significant research in the field, the Journal of Molecular Spectroscopy is an invaluable resource for astrophysicists, chemists, physicists, engineers, and others involved in molecular spectroscopy research and practice.
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