PECULIARITIES OF THE ELECTRONIC AND ELECTRON VIBRATIONAL-SPECTRA OF ORGANIC CONDUCTORS - BEDT-TTF SALTS OF ALPHA-TYPE STRUCTURE

Polarised infrared reflectivity spectra of some ET-based conducting sa lts of alpha-type structure are measured and compared: (ET)(2)I-3 (I), (ET)(2)TlHg(XCN)(4) (X S, Se) (II) and (ET)(8)[Hg4Br12(CH3C6H4Cl)(2)] (III). For both I and II the electronic reflectivity is greater for t he polarisation perpendicular to ET stacks. However, a resolved electr on vibrational band in the region of 1 100-1 400 cm(-1) is observed fo r II in the polarisation characterised by lower electronic reflectivit y in contrast with the spectra of I. Another difference between I and II is the absence of the pronounced plasma edge in the region of 4 000 cm(-1). In the spectre of II, which may be due to high electron dampi ng. For III the electronic reflectivity is low and no resolved electro n vibrational band in the region of 1 100-1 400 cm(-1) is obsenred The peculiarities of the electron-vibrational spectra of I, II and III ma y be due to the details of the crystal structure. (C) 1997 by John Wil ey & Sons, Ltd.