Torsion–Rotation Energy Levels and the Hindering Potential Barrier for the Excited Vibrational State of the OH-Stretch Fundamental Band ν1of Methanol

✍ Scribed by R.H. Hunt; W.N. Shelton; Francis A. Flaherty; W.B. Cook

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 691 KB
• Volume: 192
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1998.7689

✦ Synopsis

The absorption spectrum of methanol vapor has been recorded at room temperature from 3200 to 4200 cm Ϫ1 with a 1.24-M path-difference Fourier transform spectrometer. Over 10 000 transitions to the torsion-rotation states n, J, K of the OH stretching fundamental band 1 have been assigned, thereby greatly expanding the results of previous investigations. Approximately 4000 of the cleaner lines have been used to determine 665 excited state torsion-rotation levels with principal torsional quantum number n ϭ 0 as well as 494 levels with n ϭ 1, 286 levels with n ϭ 2, and 14 levels with n ϭ 3. These levels correspond to 86 values of the quantum numbers n, , K. Most of the levels of a given n, , K are perturbed resulting in irregular P-, Q-, and R-branch series. The J ϭ 0 origins for 64 values of n, , K have been fitted and a value of 410 cm Ϫ1 obtained for the hindering potential barrier. This is in agreement with a previous study of grating spectra but is lower than that obtained in more recent analyses of n ϭ 0 4 0 transitions observed for K Յ 3 in very low temperature spectra. The criteria used here to select states to be fitted and the difficulties in estimating the J ϭ 0 origins because of the many perturbing level crossings are discussed.