Optical conductivity to probe boson structure

The phonon structure in optical data can be inverted to obtain the transport electron-phonon spectral density alpha(2) F-tr(omega). For more general electron-boson exchange models we test the accuracy of using Allen's approximate relationship between spectral density and optical scattering rate instead of complete Eliashberg equation results. Both, s-wave and d-wave superconducting gap symmetries are considered. (C) 2006 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim.