RESONANCE RAMAN INVESTIGATIONS OF LOW ENERGETIC MODES IN THE ORGANIC SUPERCONDUCTORS ALPHA(T)-(BEDT-TTF)(2)I-3 AND BETA-(BEDT-TTF)(2)IAUI

A study of low energetic modes in the resonance Raman spectra of the o rganic superconductors (alpha(t)-(BEDT-TTF)(2)I-3 (T-c = 8 K) and beta -(BEDT-TTF)(2)IAuI (T-c = 4 K) in the temperature range of 1.5-100 K w as performed. In both materials, a strong vanishing of low energetic p honon bands at 30 cm(-1) and 40 cm(-1) for alpha(t)-(BEDT-TTF)(2)I-3) and at 27 cm(-1) and 33 cm(-2) for beta-(BEDT-TTF)(2)IAuI below T-c wa s observed. For the symmetric stretching mode of the I-3(-) and the IA uI- anion at 120 cm no change below T-c was found. In addition, wavele ngth dependent measurements on (alpha-(BEDT-TTF)(2)I-3 were performed, indicating that the modes around 30 cm(-1) are probably librational m odes of the BEDT-TTF molecules.