FAR-INFRARED PERMANENT AND INDUCED DIPOLE ABSORPTION OF DIATOMIC-MOLECULES IN RARE-GAS FLUIDS .2. SPECTRAL THEORY

We present a spectral theory for the far-infrared absorption spectrum of a very diluted solution of diatomic molecules in a rare-gas fluid, that includes permanent and induced contributions. The absorption coef ficient is given as the convolution of a translational spectrum and a rotational spectrum. The former is described in terms of time correlat ion functions associated to the induced dipole moment. The latter is d iscussed on the basis of a model consisting of a quantum rigid rotor i nteracting with a thermal bath, making use of time correlation functio ns associated to the different anisotropic orders of the solute-solven t intermolecular potential. Non-Markovian and line mixing effects are taken into account. Explicit expressions for the five leading contribu tions of the induced dipole moment are given. (C) 1995 American Instit ute of Physics.