Photodissociation of CH3I/Cu(1 1 0)–X (X = I, Cl) at λ=308 nm: control of photodissociation dynamics by surface environment

The λ=308 nm photodissociation of CH3I adsorbed on a Cu(1 1 0)–I surface displays perturbed dynamics as compared to gas-phase CH3I at similar wavelengths. In neutral photolysis CH3I can dissociate along one of two pathways to form CH3+I(2P3/2) or CH3+I∗(2P1/2). In the initial laser pulses incident upon CH3I/Cu(1 1 0)–I approximately 80% of the molecules proceed along the CH3+I∗ pathway, with this fraction diminishing to ∼20% as the surface photodissociation proceeds. This is evidence that the local surface environment is perturbing the CH3I species during dissociation, and reveals the potential to control the dissociation process by a tailored surface environment. Further evidence of the crucial role of surface environment affecting the CH3I photodissociation process is found for CH3I adsorbed on Cu(1 1 0)–I and Cu(1 1 0)–Cl surfaces, in which the CH3 photoproduct yield varies widely depending upon the surface preparation.