Infrared photoacoustic studies of SF6 and NH3 adsorption on silver films characterized by XPS have been performed under UHV conditions with a tunable CO2 laser. The results clearly demonstrate submonolayer surface sensitivity of the photoacoustic technique. Studies of both gas-surface systems further illustrate the simplicity and general applicability of this surface vibrational technique. © 1983, American Vacuum Society. All rights reserved.