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)TIHg(XCN)(4) (XS,Se) (II) and (ET)(8)[Hg4Br12(CH3C6H4CI)(2)] ( III). For both I and II the electronic reflectivity is greater for the polarisation perpendicular to ET stacks. However, a resolved electron vibrational band in the region of 1 100-1 400 cm(-1) is observed for II in the polarisation characterised by lower electronic reflectivity 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 c m(-1) in the spectra of II, which may be due to high electron damping. For III the electronic reflectivity is law and no resolved electron v ibrational band in the region of 1 100-1 400 cm(-1) is observed. The p eculiarities of the electron-vibrational spectra of I, II and III may be due to the details of the crystal structure. (C) 1997 by John Wiley & Sons, Ltd.