Infrared spectroscopy of Ne– 12C 18O 2 and Xe– 12C 18O 2: Change in the CO 2 intramolecular potential by formation of rare gas–CO 2 complexes

Abstract

High-resolution infrared spectra of Ne– 12C 18O 2 and Xe– 12C 18O 2 have been observed in the ν 3 band (2314 cm −1) region of 12C 18O 2 by diode laser absorption spectroscopy of a pulsed molecular beam. The vibrational band origins and rotational constants for these complexes are obtained. The observed shifts of the ν 3 band origin for Rg–CO 2 (Rg = Ne, Ar, Kr, Xe) with respect to that of CO 2 exhibit a systematic 16O– 18O isotope effect excepting a significant deviation for Ne–CO 2 from a regular trend. This apparent anomaly is interpreted in terms of a change in the intramolecular potential function of CO 2 caused by complex formation.