Photodissociation of CH_3Cl, C_2H_5Cl, and C_6H_5Cl on the Ag(111) surface:Ab initio embedded cluster and configuration interaction study

摘要

We report a comparative study of the photoinduced C—Cl bond cleavage in three Rd—C1molecules (Rd=CH_3, C_2H_5, andC_6H_5radicals) on the Ag(111) surface. The ground, lowest excitedstates as well as anion states of adsorbed molecules have been computed at their equilibriumgeometry and along the C—Cl dissociation pathway using the ab initio embedded cluster andmultireference configuration interaction methods. The anion state can be formed by photoinducedelectron transfer from the substrate to an adsorbate and is strongly bound to the surface in contrastwith the electronic states of the adsorbate itself, which are only weakly perturbed by the silversurface. The excitation energy of the anion state lies lower in the Franck—Condon region than thatof the lowest singlet excited state for all adsorbates and correlates directly with the dissociationproducts: adsorbed chlorine atom and the gas phase or adsorbed radical for Rd=CH_3, C_2H_5, andC_6H_5,respectively. The computed redshift of the photodissociation spectrum for thesubstrate-mediated photodissociation process relative to the corresponding gas-phase reaction is~2 eV for CH_3Cl and C_2H_5Cl, ~1 6H_which result is in good agreement withexperimental data.