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Catalysis Letters Vol. 76, No. 12, 2001 35 Second order isothermal desorption kinetics

Summary: Catalysis Letters Vol. 76, No. 12, 2001 35
Second order isothermal desorption kinetics
Y. Lilach, I.M. Danziger and M. Asscher
Department of Physical Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel
Received 22 March 2001; accepted 20 June 2001
A new method is presented to analyze recombinative desorption from surfaces in an isothermal mode. The activation energy for
desorption obtained this way is accurate as long as it is coverage independent. Second order recombinative desorption experiments of 15N2
and D2 from Ru(001) were used to demonstrate this method. The activation energies were Ea(N2) = 48 2 kcal/mol and Ea(D2) =
22 1 kcal/mol for coverages below 0.1 and 0.2 of saturation coverage, respectively. Studying N/Ru(001) provides evidence for bulk
nitrogen atoms that slowly diffuse to the surface leading to isotope scrambling.
KEY WORDS: isothermal desorption; second order kinetics; recombinative desorption
1. Introduction
Temperature-programmed desorption (TPD) is one of the
basic experimental tools of surface science for the identifica-
tion of desorbing species, and for obtaining their desorption
kinetics. Comprehensive reviews on the subject exist in the
literature [1,2]. Many decades after it was first introduced,
new methods are still being developed to improve its ana-
lytical power, for example FDS (fractional desorption spec-
troscopy) [3] which utilizes cycles of controlled heating and


Source: Asscher, Micha - Institute of Chemistry, Hebrew University of Jerusalem


Collections: Chemistry