PERMANENT AND INTERACTION-INDUCED FAR-INFRARED SPECTRA OF CO IN DENSEAR - A MOLECULAR-DYNAMICS APPROACH

Permanent and electric multipole induced contributions to the far-infr ared absorption spectrum of CO in Ar for dense gas and liquid densitie s have been calculated by means of classical molecular dynamics simula tions. The comparison of the simulated spectra with experiments let us to give an estimation of some multipole moments of CO: quadrupole, oc tupole and hexadecapole. Although the experimental profiles lack of a fine rotational structure: the results of the simulations and their co mparison with previous theoretical works, indicate that at low tempera tures, the consideration of a quantum time correlation function for th e dipole moment is necessary to get a good agreement with experiments. Finally, it is shown that the permanent-induced and induced-induced c ross terms in the absorption coefficient, that usually are difficult t o calculate from a theoretical viewpoint, are not very relevant for th is system.