QUANTITATIVE EXTRACTION OF CONTINUOUS DISTRIBUTIONS OF ENERGY-STATES AND PREEXPONENTIAL FACTORS FROM THERMAL-DESORPTION SPECTRA

In many adsorption systems of practical interest, such as polycrystalline surfaces, desorption occurs from a continuous distribution f(E) of energy states. The quantitative inversion of temperature programmed desorption (TPD) spectra to obtain f(E) has heretofore proven quite difficult. In this paper, a method is presented in which f(E) may be calculated from a single spectrum for any reaction order if the pre-exponential factor upsilon(0) is known. If upsilon(0) is not known a priori, it is shown how a conventional heating rate study may be used to determine the magnitude of upsilon(0) and any energy dependence it may have. Some aspects of the coverage dependence of the desorption parameters may be determined as well.