The Scattering of Light II. The Complex Refractive Index of a Molecular Fluid
Abstract
We treat the complex refractive index of a finite molecular fluid on the basis of a classical manybody theory; the surface problem is handled through surfacedependent propagators. We develop a density expansion generalizing the LorentzLorenz relation and sum all twobody terms to a closed form with intermolecular correlations determined by a LennardJones pair potential; the dependence on density, temperature and frequency is discussed and the case when the frequency is near a molecular resonance is considered. The refractive index and the extinction coefficient are compared with experiments for gases. We also derive a generalization of the macroscopic relation of Onsager and Bottcher from the manybody theory, essentially as an expansion in an effective polarizability of a molecule in the manybody system. Exact microscopic expressions for an effective polarizability and for a reaction field are identified, and it is shown that they are related like the Bottcher polarizability and the Onsager reaction field in a welldefined decorrelation approximation. The relation with, and validity of, the macroscopic formulae of Lorentz and Bottcher are analysed in depth.
 Publication:

Philosophical Transactions of the Royal Society of London Series A
 Pub Date:
 February 1987
 DOI:
 10.1098/rsta.1987.0017
 Bibcode:
 1987RSPTA.321..305H