COMPUTER-SIMULATION OF THE FAR-INFRARED COLLISION-INDUCED ABSORPTION-SPECTRA OF GASEOUS CO2

Far infrared collision induced absorption spectra of gaseous CO2 were computed using molecular dynamics simulations. The quadrupole and hexa decapole multipolar induction, through the trace, and the anisotropy o f the molecular polarizability were found to be insufficient to repres ent properly the dipole induction mechanism. For a detailed analysis o f the induction process the spectra obtained were decomposed into comp onents resulting from different terms of the induced dipole. Based on this decomposition, an additional overlap contribution for each term w as proposed. When spectra were recomputed including such overlap, good agreement between experiment and simulation was achieved over the tem perature range at which measurements exist (233-400 K). The use of an anisotropic intermolecular potential was found to be of crucial import ance for obtaining the right shape of the far wings of the spectra.