Low-temperature softening of some Raman modes in BEDT-TTF and d 8-BEDT-TTF

Abstract

We report the temperature-dependent frequencies of the strong features in the Raman spectra of neutral BEDT-TTF and d 8-BEDT-TTF. We note an unusual softening of the features due to the modes involving the C–H vibrations in the terminal ethylene groups, as well as one mode involving the central double-bonded carbon atoms. We relate these softenings to the increased bending of the neutral molecule at low temperatures.