Proposed Technique for Surface Dynamics Measurements at High Pressure

Abstract

A new experimental technique is described in which dynamic processes on surfaces—adsorption, desorption, and diffusion—can be monitored directly. The shift in frequency of resonant surface vibrations in a crystal is monitored as a function of time while the surface is exposed to a time dependent driving force. This surface acoustic wave (SAW) device is capable of resolving changes in surface concentrations of less than 1% of a monolayer over time spans of milliseconds or longer, under pressure conditions ranging from ultra-high vacuum to moderate-to-high pressure. The development of the SAW as a monitor for dynamic processes will help meet the instrumental needs for studying the fluid-solid interfaces which control many separation processes.