Photodissociation cross sections of N2O3 adsorbed on An(III)

The photochemistry of N2O3 adsorbed on a Au(111) surface has been studied a t < 100 K, N2O3 is prepared by a reaction of NO2 chemisorbed on a Au surfac e with gas-phase NO. The adsorption states of N2O3 are characterized by IR reflection-absorption spectroscopy. Adsorbed N2O3 is found to undergo rapid photodissociation to form chemisorbed NO2 and gas-phase NO under UV and vi sible illumination. The photodissociation cross section is determined to be (3.0 +/- 1.8) x 10(-17) cm(2) at 350 nm, which is much greater than the ma ximum absorption cross section of gas-phase N2O3 and one of the highest val ues ever observed for photochemical reactions on a metal surface. The spect ral profile of the NO yield is significantly shifted to longer wavelengths as compared to the absorption spectrum of gas-phase N2O3. The significant r ed shift of N2O3 absorption in aromatic solvents suggests that electron tra nsfer from the surface to N2O3 enhances the absorption cross section of ads orbed N2O3 at longer wavelengths.