Optical parameters from reflectance data. A new and versatile approach

A method is described which can replace both a Kramers-Kronig and a dispersion analysis as a means of obtaining optical parameters from reflectance data of condensed systems. It has advantages whenever a large number of data points must be sampled and when the absorption band profile is used to interpret quasiparticle dynamics. The efficiency of the method arises because evaluation of the phase shift upon reflection is better performed by multiplication in the time domain than by convolution in the frequency domain as is done by a Kramers-Kronig method. The efficiency of the method is illustrated and using reflectivity data of an anthracene crystal, the errors in its use, while still comparable to the less efficient traditional methods are shown to be insignificant compared with the experimental errors in such data.