The photochemistry of monolayer methyl iodide (CH3I) on a silver-covered TiO2(110) surface is studied by X-ray photoelectron spectroscopy (XPS). Upon the UV irradiation of CH3I/Ag/TiO2(110) at a cryogenic temperature, methyl iodide undergoes desorption and dissociation. The cross sections for CH3I dissociation and desorption are measured at different photon wavelengths of 251, 290, 312, 364, 403, and 546 nm. The photochemistry of monolayer CH3I on Ag/TiO2(110) is wavelength dependent. While photodissociation is the predominant mechanism for CH3I depletion upon irradiation with large-wavelength lights, the nonthermal photodesorption of molecular CH3I becomes the major process at wavelengths below 312 nm. The desorption of energetic CH3 fragments following CH3I photodissociation is evident. Possible mechanisms for the present photochemistry of CH3I on Ag/TiO2(110) are discussed and compared with those on the Ag(111) and TiO2(110) surfaces.

The thermal reactions and photochemistry of monolayer methyl iodide (CH 3 I) on a silver covered TiO 2 (110) surface have been studied using combinative techniques of temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS). About~60% of CH 3 I at monolayer coverage on Ag/TiO 2 (110) dissociates between 130 and 200 K yield adsorbed CH 3 and I, with the rest desorbing molecularly at a peak temperature of 200 K in a TPD study. Photochemistry of CH 3 I on Ag/TiO 2 (110) is wavelength dependent. Irradiation of monolayer CH 3 I by 404 nm photon causes C-I bond dissociation and CH 3 desorption. Upon 290 nm, UV irradiation, the depletion of CH 3 I (a) is dominated by photodesorption of molecular CH 3 I.