High-Resolution Infrared Spectroscopy of Methyl Isocyanide: The ν3, ν6, and ν7 + ν8 Bands

✍ Scribed by L. Le; J. Pliva; L.P. Gold; R.A. Bernheim

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 413 KB
• Volume: 170
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1995.1088

✦ Synopsis

The vibration-rotation spectrum of methyl isocyanide (\left(\mathrm{CH}{3} \mathrm{NC}\right)) has been recorded with the aid of a high-resolution Fourier transform spectrometer in the region (1370151560 \mathrm{~cm}^{-1}) containing the perpendicular band of the fundamental vibration (v{6}) (species (E) ), the weaker parallel band of the (\nu_{3}\left(A_{1}\right)) fundamental, and the perpendicular combination band (\nu_{7}^{\mp}+\nu_{B}^{\mp}(E)) enhanced by Fermi resonance with (v_{6}). Sixteen hundred seventy well-resolved lines were assigned to 15 subbands of (\nu_{6}, 6) subbands of (\nu_{3}), and 3 subbands of (\nu_{7}^{-}+\nu_{8}^{-}). A strong (x, y)-Coriolis resonance between (\nu_{3}) and (\nu_{6}) and Fermi resonance between (\nu_{6}^{ \pm})and the (E) component (\nu_{7}^{\mp}+\nu_{8}^{\mp}), as well as between (\nu_{3}) and the (A_{1,2}) components (\nu_{7}^{ \pm}+\nu_{8}^{\mp}), greatly affects the spectrum. Additional weaker anharmonic interaction of (\nu_{6}) with the (\nu_{4}+2 \nu_{8}^{2}) combination and higher-order rotational interactions connecting the various states were also detected in the spectrum. All of these interactions have been incorporated into a (9 \times 9) Hamiltonian matrix used for modeling the upper states of the observed transitions. A set of spectroscopic constants is reported for the upper states of the bands (\nu_{3}, \nu_{6}), and (\nu_{7}+\nu_{8}) and for (\nu_{4}+2 \nu_{8}^{2}), which reproduces the observed lines with an overall standard deviation of 0.0012 (\mathrm{cm}^{-1}). 1995 Academic Press. Inc.