Raman studies in CuTCNQ: Resonance Raman spectral observations and calculations for TCNQ ion radicals

摘要

The Raman spectra of thin film, and powdered crystalline forms of CuTCNQ have been studied and analyzed in connection with their electronic spectra and vibrational normal coordinate analysis and molecular orbital results. Nonresonance and resonance Raman conditions have been obtained by using different sample forms and source wavelengths. Shifts of TCNQminus;and TCNQ=vibrational frequencies from those of TCNQ0due to changes in the charge on the TCNQ moiety have been calculated in terms of molecular orbital parameters and TCNQ0vibrational frequencies. The resonance Raman enhancement of TCNQminus;in the red band system is shown to be of Franckndash;Condon origin and its resonance Raman spectrum in this region is calculated. Transformation of CuTCNQ to TCNQ0with different laser lines is explained on the basis of photoinduced electronic transitions.