Automatic ellipsometer with high sensitivity and special advantages for infrared spectroscopy of adsorbed species.

An automated ir ellipsometer for measurements of the optical properties of thin adsorbed films is described. The instrument makes use of two stationary polarizers that bracket a rotating polarizer and the reflecting surface. This combination introduces modulation in the transmitted light intensity at twice and four times the frequency of rotation of the polarizer. The phases of these two frequency components are then measured in digital form relative to signals derived from the rotating device, the entire instrument being under automatic data acquisition control. A result for an ir ellipsometric study of formic acid chemisorbed on silver is presented.