OPTICAL-PROPERTIES OF ORGANIC CONDUCTOR (ET)(4)HG3I8 - ALTERNATIVE TYPE OF ELECTRON-VIBRATIONAL INTERACTION

The reflectivity spectra of single crystals of (ET)(4)Hg3I8 and (d(8)- ET)(4)Hg3I8 were studied. In contrast with earlier studied clorine- an d brominemercurate compounds of the series (ET)(4)Hg-3-delta-X(8) (X = Cl, Br, I), the spectra of iodinemercurate compounds exhibit low refl ectivity without well-defined plasma edge and without electron-vibrati onal bands in the region 1 000-1 400 cm(-1). The latter fact may be du e to electron-vibrational interaction with non-totally symmetric modes which may originate from peculiarities of crystal structure of iodine mercurate compounds. A phase transition of the first type is observed both for (ET)(4)Hg3I8 and (d(8)-ET)(4)Hg3I8. At the transition tempera ture a jump in conductivity and reflectivity is observed.