Discovery of vibronic effects in the Raman spectra of mixed-stack charge-transfer crystals

By studying the tetrathiafulvalene-chloranil (TTF-CA) complex the different of electron molecular-vibration (e-mv) interactions in the Raman and infrared spectra of mixed-and segregated-stack one-dimensional compounds are compared and interpreted. In mixed-stack crystals, besides the well-known infrared effects, the vibronic coupling causes a shift of the Raman frequencies. From this previously unobserved effect the e-mv coupling constants of TTF and CA are evaluated. © 1982 The American Physical Society.