Direct evidence of lattice-relaxed charge transfer exciton strings

We report first direct evidence, by X-ray diffuse scattering, of lattice-relaxed charge transfer exciton strings, which are one-dimensional self-trapped multiadjacent excitons. These non-linear excitations are key objects in quasi-one-dimensional organic compounds that undergo the neutral-ionic transition and are responsible for their physical properties. The one-dimensional fluctuations are very well described within the framework of the transfer integral method and physical parameters are deduced from both X-ray and dielectric measurements.