Low-temperature infrared and raman spectra of the organic superconductor /spl kappa/(BEDT-TTF)Cu[N(CN)/sub 2/]Br, containing selected ISO topic substitutions of /sup 13/C and /sup 34/S, compared with normal-coordinate calculations

Summary form only given. We will present measurements of the polarized infrared and Raman spectra, as a function of temperature, of single crystals of pure and isotopically-substituted /spl kappa/-(BEDT TTF)Cu[N(CN)/sub 2/)Br. The isotopically-substituted samples contain either /sup 13/C at the two central bond locations, or /sup 13/C at the six locations in the TTF framework, or /sup 34/S at the eight locations in the ET molecule. The measured frequency shifts will be used to aid in mode assignments and to refine the normal-coordinate calculations. Comparison between the infrared and Raman spectra will allow us to calculate electron-phonon couplings. The Raman spectra are obtained with a Fourier-Transform Raman spectrometer using an infrared laser. This reduces both the fluorescence background radiation and the possibility of photodegradation of the organic samples.