Absorption Corrections and Concentration Optimization for Absorbing Samples in Resonance Raman Spectroscopy

Abstract

For Raman scattering studies of absorbing samples, e.g., in resonance Raman spectroscopy, it is frequently important to optimize the concentration and to correct for self-absorption effects on the observed intensities. These question are explored for 90° “transverse” scattering in a 0.1-cm capillary through intensity measurements of resonance Raman bands of ferro-cytochrome c and tris(1,10-phenanthroline) iron (II). It is found that a simple log intensity vs concentration plot provides the extrapolation needed to eliminate self-absorption effects. The optimum concentration is found to correspond to an absorbance per 1 cm of path length of 13 (average of values for the incident and scattered wavelengths) and is independent of absorptivity and of refractive index of the medium. The data are adequately reproduced by a point-scattering model, although different values of the effective light path through the sample are required to fit the self-absorption and intensity vs concentration curves.