Fully resonant CARS of cresyl violet in polyacrylic acid polymer films

Abstract

Abstract Multi-resonant CARS data for ground and excited electronic state resonances (593.585 cm−1) of cresyl violet perchlorate in polyacrylic acid are reported. The intensity of the excited state resonance (585 cm−1) depends on the location of the ω1-field (ωas = 2ω1 − ω2) within the severely inhomogeneously broadened absorption profile of the dye. Non-photochemical hole burning is used to determine the vibronic transitions which contribute to the absorption profile. It is argued that the linear electron-phonon interaction is an important mechanism for producing an egalitarian distribution of excited dye sites with a population sufficiently high to permit observation of the excited state resonance. A marked non-photochemical hole burning effect on the intensities of the CARS resonances is used for the assignment of 585 cm−1 as an excited state resonance. The absence of line narrowing in the CARS and CSRS spectra is reported and discussed. Finally, a novel narrowing of the 593 cm−1 ground state resonance with increasing temperature is reported and shown to occur only for restricted values (frequency) of ω1.