CORRELATION OF PHOTOELECTRON YIELDS AND PHOTODISSOCIATION RATES OF CH3CL ON PT(111) AND CARBON-COVERED PT(111)

Photoelectron yields, as a function of coverage, were measured during UV irradiation (<5.4 eV) of CH3Cl adsorbed on Pt(111) and C-covered Pt(111) and were correlated with initial photodissociation rates. For each coverage, the initial rates were measured by the time-dependent loss of CH3Cl. These rates were analyzed by using a simple model that assumes the process is first order with respect to both CH3Cl coverage and the number of photoelectrons. An excellent correlation was found for C-covererd Pt(111) over the entire coverage range, while some deviation in the submonolayer region was observed for C-free Pt(111). The constant rate coefficients in the multilayers for both surfaces, and their equality for both, confirm that photoelectrons play a dominant role. The enhancement for lower coverages on Pt(111) is discussed. © 1990 American Chemical Society.