THEORETICAL FAR-INFRARED SPECTRA OF CO IN AR GAS

The permanent dipolar contribution to the far-infrared absorption spec tra of CO in Ar gas at various densities has been calculated. A non-Ma rkovian spectral theory described in terms of time correlation functio ns associated to the two first anisotropic orders of the intermolecula r potential is used. Comparison with experimental spectra shows that t he permanent dipolar contribution provides practically the whole absor ption at low densities, for which the spectrum exhibits a clear line s tructure, but not at high densities well after the rotational line str ucture is missing from the absorption profile.