Structural Instabilities of Molecular Conductors Studied By Optical Spectroscopy - Phase-transitions of (dm-dcnqi)2x(x=ag,li,na,k,rb)

The ability of infrared spectra to selectively probe the temperature evolution of a 4k(F) modulation (dimerization) and a 2k(F) modulation (tetramerization) of the structure of quarter-filled organic conductors is demonstrated for the first time for the title compounds. A detailed analysis of the totally symmetric normal modes of DM-DCNQI and of their coupling to the radical electron for the isolated molecule is also reported