BULK EFFECTS IN THERMAL-DESORPTION SPECTROSCOPY

In this work we analyze Thermal Desorption Spectroscopy (TDS) experime nts of gases considering simultaneously atomic diffusion in the bulk a nd recombinative reaction on the surface of a solid sample. We perform computer simulations in a three-dimensional cubic lattice, and compar e the simulated spectra with numerical results from a simple reaction- diffusion model, and analytical results from models for the fast diffu sion and fast reaction regimes. We analyze the effects on the spectra of each relevant parameter: diffusivity, reaction coefficient, heating rate, initial concentration of particles and sample size. We also dev elop a rate-limiting step identification procedure based on the analys is of peak position as a function of initial concentration. This last procedure applied to the simulations and to experimental TDS spectra p roduces very good results. (C) 1998 American Institute of Physics. [S0 021-9606(98)50939-7].