Knowledge Bank

Fourier transform infrared absorption spectroscopy was used to investigate the rotational and vibrational cooling of a 1:1 pyridine-argon mixture in a supersonic expansion. The C-H stretching bands in the $3000cm-1$ region and the C-H out-of-plane band at $700cm-1$ were analyzed. Band contour analysis of the $700cm-1$ band indicates a rotational temperatures of $100\pm 20$ K. Consideration of the sequence band structure and isotope shifts for this band suggest a vibrational temperature of $140\pm 40$ K. The spectrum of cooled-pyridine was used by K. Wong et.$al.1$ in the vibrational assignment of the fundamentals in the C-H stretching region. A rough band contour analysis confirms these assignments.