The Interaction of CO and W(111) Surface

摘要

The adsorption of CO on W(111) surface in the range of adsorption temperature between 300 K and 1000 K has been studied using AES, LEED, and TDS in an UHV system. After CO saturation at 300 K, four desorption peaks are observed at temperatures (K) of about 400, 850, 1000, and 1100 in thermal desorption spectra, called as メ, モ1, モ2, and モ3 state, respectively. The state was attributed to molecular species of CO, which is well known. Because the CO in モstates (especially the モ3 state) is still debated as to whether it is dissociative or non-dissociative, the モ3 state is mainly discussed. By using the variation method of heating rate in the thermal desorption spectrometry, the desorption energy and pre-exponential factor for the モ3 state are evaluated to be 280 kJ/mol and 1.5】10 12 s-1 , respectively. A lateral interaction energy of 5.7 kJ/mol can also be estimated by Bragg-Williams approximation. To interpret the thermal desorption spectra for the モ3 state, moreover, those for the model of a first order and a second order desorption are simulated using quasi-chemical approximation. In this study, a model of lying-down CO species is proposed for the モ3 state of CO adsorption.