Resonance Raman scattering for mid-gap absorption bands in halogen-doped MX chains

Resonance Raman spectra for the mid-gap absorption bands were measured in chlorine-doped quasi-one dimensional [Pt(en)2][Pt(en)2Cl2](ClO4)4 (en = ethylenediamine) single crystals, in order to classify the origin of the Raman modes relevant to the photo-induced defect states. We found that the intensity of the Raman modes located between 270 and 285 cm−1 relative to that of the Raman modes between 285 and 295 cm−1 increases with increasing the chlorine doping time. This fact strongly suggests that the origin of the former Raman modes is attributed to the hole polarons and that of the latter ones is assigned to the electron polarons.