Vibrational predissociation in the CO2 dimer and trimer and rare gas–CO2 complexes

Abstract

Vibrational predissociation linewidths for the CO2 dimer and trimer and the Ne–CO2 and Ar–CO2 complexes have been resolved using a bolometer-detected (optothermal) molecular-beam color-center laser spectrometer. Observations were made on the pair of vibrations near 3715 and 3613 cm−1 corresponding to the ν1+ν3/2ν02+ν3 Fermi diad of CO2. Homogeneous linewidths of from ∼0.5 to ∼22 MHz (FWHM) were measured for these related complexes, with Ne–CO2 exhibiting both the broadest and the sharpest lines for the upper and lower bands, respectively. Ar–CO2 and (CO2)2 showed mode-independent intermediate predissociation rates while only the lower band of (CO2)3 could be found. The results indicate that V→V energy transfer processes are the dominant predissociation channels with symmetry selection or propensity rules and specific resonances playing a role.