Core Excitons in Tetrathiafulvalene-Tetracyanoquinodimethane (TTF-TCNQ)

Abstract

Inelastic electron scattering spectra of nitrogen, sulfur, and carbon core excitations in tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) are presented. The spectra exhibit sharp excitonic transitions to final states localized on separate ${\mathrm{TTF}}^{+}$ or ${\mathrm{TCNQ}}^{-}$ ions followed at higher energies by a continuum of transitions to free-electron states. In contrast to prior photoemission experiments, we find no evidence for neutral molecules in the bulk of TTF-TCNQ.