High-Resolution Vibrational Spectroscopy of trans-Formic Acid in Solid Parahydrogen

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• 作者：Leif O. Paulson ; David T. Anderson*
• 刊名：Journal of Physical Chemistry A
• 出版年：2009
• 出版时间：March 5, 2009
• 年：2009
• 卷：113
• 期：9
• 页码：1770-1778
• 全文大小：182K
• 年卷期：v.113,no.9(March 5, 2009)
• ISSN：1520-5215

文摘

We report high-resolution vibrational spectra of six normal modes of trans-formic acid (FA) in rapid vapor deposited solid parahydrogen (pH₂) with particular emphasis on the carbonyl stretching mode (ν₃) at 1770 cm⁻¹. Infrared spectra in the ν₃ and 2ν₃ regions reveal that even in 99.99% enriched pH₂ samples, residual orthohydrogen (oH₂) present in the solid preferentially clusters to FA producing measurable shifts in the ν₃ transition frequency. The individual FA(oH₂)_n cluster peaks in the size range from n = 0 to n = 5 are resolved, permitting unambiguous assignment of the ν₃ and 2ν₃ transition frequencies and linewidths for FA with a first solvation shell (n = 0) of only pH₂ molecules. This n = 0 feature is well fit by a Lorentzian line shape with a line width of 0.214(6) cm⁻¹ and 0.45(2) cm⁻¹ for ν₃ and 2ν₃, respectively, which is surprisingly broad for a small nonrotating molecule trapped in solid pH₂. Implications of the broad FA ν₃ Lorentzian line shape in terms of homogeneous and inhomogeneous broadening mechanisms are discussed.