Spectroscopy of Surface Electromagnetic Waves

A thin dielectric film deposited on a metal increases SEW attenuation which becomes stronger as eigenfrequencies of the fihn vibrations are approached. 

Modulated radiation from a tunable IR laser falls onto a prism at the condition of attenuated total reflection. Arising evanescent radiation can excite SEW on a metal surface at a suitable distance from the prism base. SEW propagates along the metal surface and can be attenuated by a thin dielectric film deposited on this metal. By means of a similar prism placed at a certain distance from the first one the SEW is transformed into normal radiation and detected by a pyroelectric detector. 

The SEW excitation efficiency is affected by both the angle of incidence in the prism and the gap height, the last being different for the coupler and decoupler prism. The size of the gap depends on the metal and the conditions of its evaporation. An absorption spectrum is obtained by a differential method in which the ratio of intensities is measured for a SEW on the metal surface with a film and without a film at various distances between the prisms. 

Very thin films of organic and inorganic substances on metal surfaces can be measured down to monolayers. 

Spin Polarised Electron Energy Loss Spectroscopy [S3, 54] 

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