A quantum electrodynamical theory of differential scattering based on a model with two chromophores I. Differential Rayleigh scattering of circularly polarized light

Abstract

Chiral systems can scatter circularly polarized photons at rates dependent on the handedness of the incident radiation. Differential intensities of Raman scattering by optically active organic molecules have been observed recently. The present work deals with the theory of both Rayleigh and Raman differential scattering by using quantum electrodynamics. The calculations of differential intensities are based on a two-chromophore model in which the chromophores, assumed to be achiral in isolation, become optically active due to their dissymmetric arrangement. Results are reported for both ‘in-plane’ and ‘out-of-plane’ polarizations of the scattered radiation. They apply to an arbitrary scattering geometry and group separation. The limiting near- and far-zone behaviour is analysed in detail. In this paper (part I), the basic theory common to Rayleigh and Raman differential scattering is presented and is then applied to the Rayleigh process. The application to the Raman process is given in part II. In the Rayleigh case, the dominant contribution to the differential effect arises from interference of second-order probability amplitudes. This term varies linearly with the inter-chromophore separation in the near-zone, but inversely in the far-zone. Higher-order corrections to the differential intensities involve coupling between the chromophores; the leading correction, involving the interference of the second- and fourth-order amplitudes, has been computed.