J. Phys. I France 4 (1994) 1461-1467
Optical properties of organic conductor (ET) 4Hg 3I 8 : alternative type of electron-vibrational interactionM. G. Kaplunov, R. N. Lyubovskaya and R. B. Lyubovskii
Institute of Chemical Physics in Chernogolovka, Russian Academy of Sciences, Chernogolovka, 142432, Russia
(Received 6 December 1993, revised 1 June 1994, accepted 7 July 1994)
The reflectivity spectra of single crystals of (ET) 4Hg 3I 8 and (d 8-ET) 4Hg 3I 8 were studied. In contrant with earlier studied clorine- and brominemercurate compounds of the series (ET) 4Hg - X 8 (X = Cl, Br, I), the spectra of iodinemercurate compounds exhibit low reflectivity without well-defined plasma edge and without electron-vibrational bands in the region 1 000 - 1 400 cm -1. The latter fact may be due to electron-vibrational interaction with non-totally symmetric modes which may originate from peculiarities of crystal structure of iodinemercurate compounds. A phase transition of the first type is observed both for (ET) 4Hg 3I 8 and (d 8-ET) 4Hg 3I 8. At the transition temperature a jump in conductivity and reflectivity is observed.
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