Measurement of Fast Desorption Kinetics of D2 from Tungsten by Laser Induced Thermal Desorption.

摘要

The laser desorption method has been shown analogous to the fast temperature jump method used for studying reactions in condensed phases, and is capable of sorting out elementary processes that have differing activation energies. The variation of total flux desorbed vs. maximum temperature reached and vs. initial surface coverage determined, gave with the aid of a model kinetic rate expression desorption rate parameters. It was shown that at rates 100,000 times faster than previous measurements the kinetics of desorption of hydrogen follows the same reaction equations. Since the desorption time is short compared to the range of desorbate flight times to the mass spectrometer detector, velocity distributions of the desorbing species were determined. This along with the surface temperature history gave additional information on the reaction rate model. In the present experiments a significant number of desorbate-desorbate collisions could occur. Corrections were made for the collisional effects in the interpretation of the data. In addition it was shown how modifications of the technique could be used to mitigate the effects of collisions. (Author)