Abstract
Polarised reflectance spectra of beta -(BEDT-TTF)2IBr2 are observed for single crystals prepared by slow diffusion and an electrochemical crystallisation method. The spectra are found to be essentially identical to each other and also very similar to those observed for the isomorphic compound beta -(BEDT-TTF)2I3 in the near-infrared region. The band width of the IBr2 salt evaluated in terms of the Drude model and the tight-binding approximation is found to be 0.63 eV which is almost equivalent to that of the I3 salt.