Infrared Spectroscopy of the Amide I Mode of N-Methylacetamide in Solid Hydrogen at 2–4 K

• Published in: The journal of physical chemistry. B Vol. 115; no. 46; pp. 13659 - 13667
• Main Authors: Paulson, Leif O, Anderson, David T
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 24-11-2011
• Subjects: Acetamides - chemistry; Amides; Anharmonicity; B: Biophysical Chemistry; Cold Temperature; Constants; Cryogenic temperature; Harmonics; Hydrogen - chemistry; Infrared spectroscopy; Physical chemistry; Spectra; Spectrophotometry, Infrared
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp204800c

We report high-resolution (0.05 cm–1) FTIR spectra of the fundamental and first overtone of the amide I mode of trans-N-methylacetamide (NMA) trapped in solid molecular hydrogen (SMH) at cryogenic temperatures with low (0.03%) and high (55%) ortho-hydrogen (oH2) concentrations. NMA-doped SMH samples with high oH2 concentrations are nearly free from inhomogeneous broadening, permitting the measured amide I homogeneous line width of 1.268(8) cm–1 to be used to place a lower limit on the vibrational lifetime of 4.19(3) ps. Direct observation of the amide I overtone allows the harmonic vibrational frequency ωe = 1726.6(5) cm–1 and the anharmonicity constant ωe x e = 8.5(2) cm–1 to be determined for NMA isolated in SMH samples with low oH2 concentrations.