IR SPECTROSCOPY OF (CO)(2) USING CONCENTRATION-FREQUENCY DOUBLE-MODULATION IN A SUPERSONIC JET EXPANSION

By means of diode laser spectroscopy we observed signals of(CO)(2) in a supersonic jet expansion. Nineteen lines of a K:2 <-- 1 transition were detected by concentration-frequency double modulation in the infrared region. This modulation technique was recently developed in our group and combines a 50% duty cycle with high repetition rates (3-8 kHz). These measurements are the first analyzed spectra of(CO)(2) and give for the first time access to the spectroscopic parameters of this dimer. These measurements suggest a crossed structure, whereas former ah initio calculations suggested a T-shaped or parallel planar structure as the equilibrium structure. These data can be considered as the first step toward an improved understanding of this molecular complex. (C) 1994 Academic Press Inc.