Linear and nonlinear (CARS) raman spectroscopic investigations of cyanine dyes

Abstract

The methanolic and methanolic aqueous or aqueous solutions of the first three representatives of the homologeous series of 3,3′-diethyl-2,2′ benzthiacyanines exhibiting an increasing dimerisation with an increasing amount of water in the solvent have been investigated by spontaneous Raman scattering and CARS with different optimum excitation frequencies. Within the accuracy of our experiments (⁺−10 cm⁻¹) there are no differences between the measured Raman wave numbers of the chromophoric system of monomers and dimers.