Raman investigations on single crystals and polycristalline pressed samples of organic superconducters

The investigation of molecular vibrations is a powerful tool which can increase our knowledge on structures and on electron molecular vibrations, which are due to charge oscillation between dimerized moIecuIes,coupled with totally symmetric intramolecular modes. Raman scattering studies account for totally symmetric vibrations. In addition, Raman spectroscopy can take advantage of resonant effects. In fact, when resonant conditions are fulfilled, selected molecular vibrations are obtained as well as information on the electronic manifold involved in the resonance process. In this paper, we report on Raman investigations of polycrystalline pressed materials of superconducting tempered -α(BEDT-TTF)2I3, called in the following, αt-{BEDT-TTF)2I3 and on untempered α(BEDT-TTF)2I3. Furthermore we report on the polarized resonant Raman scattering in the superconducting regime of (BEDT-TTF)2Cu(NCS)2 single crystals