FREE-ELECTRON LASER FOR INFRARED SEW CHARACTERIZATION SURFACES OF CONDUCTING AND DIELECTRIC SOLIDS AND NM FILMS ON THEM

The set of problems that can be solved by new very sensitive method fo r investigation of surfaces and very thin layers on solids - surface e lectromagnetic waves (SEW) spectroscopy - is presented. The field of a pplications for this method was considerably extended with the use of the free electron laser (FEL). The important role of the outstanding f acilities of FEL, namely, the broad tuning range, high power, picoseco nd pulses, narrow bandwidth of emission, well-collimated beam in SEW s pectroscopy, is outlined. Interferometric SEW experiments provide the possibility for the direct determination of the real and imaginary par ts of dielectric constants at the frequencies inside the tuning range of a FEL, avoiding the Kramers-Kronig integral transformation. It is d emonstrated by the examples of infrared absorption spectra of a monomo lecular Langmuir-Blodgett film on metal, of a metal oxide film and of polymeric films of nm thicknesses on metals (exposing the effects of c hain conformation changes induced by solid surface). In the mid- and f ar-IR the ''reststrahlen'' range optical constants of single crystals CaF2, BaF2, MgO, LiNbO3 were determined. The nonlinear spectroscopy ap plications of SEW-FEL techniques to studies of a second-harmonic gener ation (SHG) on crystal surfaces in the regime of counterpropagating SE Ws - the frequency dependence of efficiency and the influence of a thi n film deposition on a quartz surface - are described.