Polarization Dependence of Raman Scattering from a Thin Film Involving Optical Anisotropy Theorized for Molecular Orientation Analysis

Polarized Raman scattering from a thin film involving uniaxial optical anisotropy deposited on a dielectric substrate has analytically been theorized. The analyte film is modeled as a three-phase system (air/film/substrate) to calculate the electromagnetic fields of the incident and scattered light propagating across the system with an aid of the transfer matrix method to exactly take the optical anisotropy of the film into account. On the new theory, a methodology for molecular orientation analysis of an extended polymethylene chain in the film is proposed, which is employed for determination of the tilt angles of the chains in single- and five-monolayer Langmuir Blodgett (LB) films of cadmium stearate deposited on a glass plate. The results agree well with those obtained by infrared spectroscopy, which confirms reliability of the present method.