Kinetic and Experimental Basis of Flash Desorption

Abstract

Techniques are developed for deriving both qualitative and quantitative information on the kinetics of gas desorption from measurements at continuously changing temperature. First- and second-order processes can be distinguished immediately by the constancy of the end point of the former. Quantitative values for activation energy and frequency factors are deduced from the experimental time-temperature curve and the instantaneous slopes of the evolution curve, even for systems with concentration-dependent rate parameters. It is shown that for multiple desorption peaks, qualitative detection is simplified by slow heating, but may result in interconversion. The experimental basis of desorption measurements using the Bayard-Alpert gauge is also analyzed, together with artifacts arising from negative pressures, bistable gauge operation, formation of new species in the gauge, and the delay in sensing density pulses transmitted through tubes.