Pre-resonance Raman intensity studies of TCNQ and TCNQ−

Abstract Pre-resonance Raman spectra have been obtained for TCNQ and LiTCNQ in acetonitrile solution using an Ar + —Kr + laser and a tunable rhodamine 6G dye laser. Using the theory of Albrecht and Hutley, we have calculated frequency factors for the intensity variations for several symmetric vibrational modes of each molecule. The observed spectra for TCNQ and LiTCNQ with violet, blue, and green excitation give evidence for B-type resonance enhancement due to vibronic mixing between at least two violet and ultraviolet transitions. The Raman spectra for LiTCNQ with yellow, orange, and red excitation show A-type enhancement due to a single electronic excitation in the near infrared.