Polarized Two-photon Absorption Spectra of Naphthalene in Durene Single Crystal with Two Synchronized Tunable Dye Lasers

Abstract

Abstract Polarized two-photon absorption spectra of naphthalene in a single crystal of durene were observed with one and two beams of tunable dye lasers. Diagonal elements of the two-photon transition tensor were determined by one beam experiments with different incident polarizations on different faces of an oriented single crystal. The off-diagonal elements of the two-photon transition tensor were determined with two synchronized beams of different wavelengths and polarizations on the same sample. It was found that most of the vibronic states have large σLL consistent with an overall vibronic Ag symmetry and a long axis polarized 1B2u intermediate state. The intermediate states of the two-photon process of the strongest vibronic origin have been discussed on the basis of the observed values of the two-photon transition tensor elements. The band also has a small but non-vanishing off-diagonal tensor element (σLM). A crystal field perturbation due to reduced site symmetry by a B3g two-photon allowed state is postulated.