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 w ere detected by concentration-frequency double modulation in the infra red region. This modulation technique was recently developed in our gr oup 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 dim er. 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 firs t step toward an improved understanding of this molecular complex. (C) 1994 Academic Press Inc.