HREELS STUDY OF CH3I AND CH3 ADSORBED ON RH(111) SURFACE

The thermal and photochemistry of methyl iodide on Rh(111) surface has been investigated by high resolution electron energy loss spectroscop y (HREELS) supplemented by Auger electron (AES) and temperature progra mmed desorption (TPD) spectoscopies. CH3I adsorbs dissociatively at su bmonolayer coverage at 90 K and molecularly at higher coverages. The d issociation of a monolayer starts above 148 K and completes below 200 K. Illumination of adsorbed CH3I enhanced the extent of the dissociati on which is ascribed to the generation of photoelectrons. The primary products of thermal and photoinduced dissociation is adsorbed CH3'and I. A fraction of CH3 is hydrogenated to CH4 above 150 K, another fract ion exists on the surface even at 300-400 K and decomposes through the formation of CHx species to hydrogen and surface carbon. No dimerizat ion of CH3 was observed.