Molecular electronic states in charge transfer complex studied by x-ray absorption spectroscopy

摘要

The electronic states of tetrathiafulvalene (TTF:TTF = C_6H_4S_4) molecule in organic ferroelectric TTF-p-bromanil (TTF-BA:BA = C_6Br_4O_2) and TTF crystals have been investigated by x-ray absorption spectroscopy (XAS) measurement at S K-edge. We elucidated that the peak structure at 2470.5 eV directly reflects the existence of hole in the highest occupied molecular orbital (HOMO) state of the TTF molecule in TTF-BA; that is consistent with the ionic TTF molecule (TTF~+). The XAS of TTF-BA was evaluated on the basis of first-principles calculations, and the calculated spectra reproduce well the shape of experimental spectrum and the peak energy of the HOMO state.