15min:

DENNIS W. TOKARYK, Physics Department, University of New Brunswick, Fredericton, NB, Canada E3B 5A3.

C₂H is a linear radical found in a variety of terrestrial environments (flames, hydrocarbon photofragments), and is abundant in the interstellar medium. Analysis of its infrared spectrum is complicated by a low-lying electronic state A\:² , about 3700~cm^-1 above the X\:^{2 +} ground state. Strong interactions between A\:² and X\:^{2 +} make it difficult to assess the vibrational character of the upper states in observed spectra.

In the course of near-infrared laser spectroscopic studies of a methane-helium discharge, we observed a ² -² band with an origin near 6340~cm^-1. Combination difference comparisons confirmed that lower state was the 000 vibrational level of the ground state of C₂H. The upper state may be a vibrational state of X\:^{2 +}, or of A\:² if a bending vibration is involved. We will present the rotational analysis of this band, and will discuss possible vibrational assignments.