The kinetics of CO desorption from Ni(110)

摘要

The kinetics of CO desorption from clean Ni(110) have been measured by thermal desorption mass spectrometry (TDMS) using the method of variation of heating rates. Analysis of the desorption spectra gives the coverage dependence of the preexponential factor ngr;d, and the activation energyEd, of the desorption rate constant. For 0thgr;0.5,Edis constant at 30.6 kcal/mol, allowing analysis of the coverage dependence of the preexponential factor under conditions where the compensation effect is absent. We observe only small changes in the preexponential factor under these conditions, where loglsqb;ngr;d(sminus;1)rsqb; rises slowly from 14.6 to 15.3 from 0thgr;0.65. Near thgr;=0.8, a synchronous drop in ngr;dby 0.6 orders of magnitude and inEdby 5 kcal/mol is observed at the onset of formation of the (2times;1)p2mgstructure. These results are discussed in light of the structures of CO in Ni(110) and the effects of ordering transitions on the desorption kinetics. The experimental results for ngr;d(thgr;) are compared with those predicted for desorption by three precursor mechanisms and for desorption of a lattice gas with lateral interactions.