From abstract: "The adsorption of ethane, ethylene and acetylene on clean iridium in a field emission microscope has been found to cause characteristic changes in the work function of the iridium surface. Further changes, which are time and temperature dependent, result when such surfaces are heated. Flash filament experiments have shown that the changes in work function upon heating are due to desorption reactions and that the desorbed product consists principally of hydrogen. By assuming a linear relationship between surface coverage and work function, it has been possible to determine the desorption kinetics from the observed rates of work function change at various temperatures. The results are consistent with a mechanism involving stepwise surface dehydrogenation in which a pair of hydrogen atoms is removed from the hydrocarbon molecule in each step, followed by desoption of the adsorbed hydrogen. At very high temperatures the remaining carbon atoms are removed, presumably by evaporation."