Calculation on Optical Effect of Matter from First Principles Using Group Theoretical Techniques

摘要

Scattering of light by molecules is commonly dealt with through Rayleigh-Debye theory. Such approach is known to be applicable to molecules whose effective index of refraction is close to unity and to imply a number of approximations which may have rather severe effects. In this paper we face the problem by adapting the method devised by Johnson, and successfully used to calculate the electronic states of large molecules, to the scattering of electromagnetic waves. Accordingly, we model a molecule as a cluster of spherical scatterers, possibly of different radii and refractive indexes. A plane electromagnetic wave, incident to the cluster, undergoes multiple scatterings which we account for by expanding the scattered wave in a multicentered series of vector harmonics. The expansion coefficients turn out to be the solutions of the system of linear equations obtained by expanding both the incident field and the within the spheres in a series of vector harmonics, and imposing the boundary conditions across the surface. Due to the presence of the incident plane wave, the above system is nonhomogeneous.