Conformation Resolved Induced Infrared Activity: trans- and cis-Formic Acid Isolated in Solid Molecular Hydrogen

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• 作者：Leif O. Paulson ; David T. Anderson ; Jan Lundell ; Kseniya Marushkevich ; Mia Melavuori ; Leonid Khriachtchev
• 刊名：Journal of Physical Chemistry A
• 出版年：2011
• 出版时间：November 24, 2011
• 年：2011
• 卷：115
• 期：46
• 页码：13346-13355
• 全文大小：950K
• 年卷期：v.115,no.46(November 24, 2011)
• ISSN：1520-5215

文摘

We report combined experimental and theoretical studies of infrared absorptions induced in solid molecular hydrogen by different conformers of formic acid (HCOOH, FA). FTIR spectra recorded in the H₂ fundamental region (4120鈥?160 cm^鈥?) reveal a number of relatively strong trans-FA induced Q-branch absorptions that are assigned by studying both FA-doped parahydrogen (pH₂) and normal hydrogen (nH₂) samples. The induced H₂ absorptions are also studied for HCOOD doped nH₂ crystals for both the trans and cis conformers that show resolvable differences. Samples containing >90% of the higher energy cis-HCOOD conformer are produced by in situ IR pumping of the OD stretching overtone of trans-HCOOD using narrow-band IR light. Minimum energy structures for 1:1 complexes of H₂ and FA are determined using ab initio methods. The measured differences in the cis- versus trans-HCOOD induced spectra are in qualitative agreement with the frequencies and intensities calculated for the identified cluster structures as discussed in terms of the model of specific interactions.