Interferometric measurements of phase shift in the IR reflection-absorption spectroscopy

Infrared reflection-absorption spectroscopy (IRRAS) r11 is widelyused to study surfaces. In this technique the reflectivity of p-polarizedradiation or its ratio to the reflectivity in s-polarization is measuredat grazing incidence. However the only measured value is not enough todetermine optical constants without using any model for frequencydependence of the dielectric function of the material under study.In the spectroscopy of surface electromagnetic waves (SEW) suchproblem is solving using interferometric measurements [2]. Although forwell conducting metals SEW spectroscopy is more sensitive [3] but formetals with low conductivity this advantage is disappeared [4]. So tostudy various metals in optimal conditions it seems to be very useful tocombine both techniques in one unit and to switch them according withsample under study. Such combining is possible using aperture excitationof SEW [3,5]. In this case at small coupling gap between the screen andthe metal surface SEW excitation takes place but for larger gaps theefficiency of SEW excitation is small [6] and we have only IRRAS signal.