The torsional vibration of the CO2-N2O complex determined from its infrared spectrum

Abstract

The spectra of the weakly bound complex CO2- N2O are studied in the regions of the ν1 and ν3 fundamentals of N2O and the ν3 fundamental of CO2 using a rapid-scan tunable diode laser spectrometer to probe a pulsed supersonic jet expansion. Five bands are measured and analyzed, of which four have not been previously studied. Two bands at 2225.75 and 1279.58 cm-1, with a/b -type rotational structure, are assigned to the ν1 and ν3 fundamentals of the N2O component of the complex. Small perturbations are noted in the ν3 band, similar to those observed previously for the nonpolar dimer (N2O)2 in the ν3 and ν1 + ν3 regions. The previously known band at 2348.86 cm-1 in the region of the ν3 CO2 stretch is analyzed in improved detail. Weaker c -type bands at 2251.46 and 2374.67 cm-1 are assigned as combinations of the intermolecular torsional (out-of-plane) vibration plus the N2O ν1 and CO2 ν3 stretches, respectively. The resulting torsional frequency of CO2- N2O is experimentally determined for the first time to be 25.8 cm-1. © 2008 American Institute of Physics.