ON THE REFLECTIVITY DISCONTINUITY GENERATED BY CRITICAL ADSORPTION ATTHE LIQUID-VAPOR INTERFACE

The reflectivity discontinuity arising from the concentration profile at critical adsorption at the Liquid-vapour interface is interpreted i n terms of the spectral properties of a potential well. When the well is soft enough at the top, the spectrum of bound states becomes contin uous and reflectivity resonances caused by the potential well become a discontinuity. In order to apply this property to the true interactio n potential between radiation and sample, we use a theorem of Abeles r elating the reflectivity of a potential function to the reflectivity o f a corresponding symmetric potential well.