THEORY OF OPTICAL-ABSORPTION DUE TO INFRARED-ACTIVE PHONONS IN DOPED C-60

We give a theory of infrared absorption due to phonons for a general e lectron-phonon coupled system. This is expressed in terms of three phy sically important parameters for each infrared active phonon mode: dim ensionless electron-phonon coupling constant lambda(alpha), renormaliz ed phonon frequency Omega(alpha), and damping parameter Gamma(alpha). We apply this theory to a molecular solid, doped fullerenes, to extrac t these parameters by fitting to experimental infrared absorption data .