Photolysis of chemisorbed dioxygen on Pd(111): Dependence on photon energy

Photolysis of chemisorbed dioxygen bound in the peroxo and superoxo configurations to Pd(111) has been studied and cross section vs photon energy measurements have been made. Three photoprocesses occur: (1) photodesorption of O2(g); (2) photoconversion between different O2(a) species; and (3) photodissociation to produce O(a). The threshold photon energy for O2(a) photodesorption or photoconversion is 3.4±0.3 eV or lower; for photodissociation of O2(a) to produce O(a), the threshold photon energy is 3.7±0.3 eV. The cross sections for photodissociation and photodesorption of chemisorbed dioxygen on Pd(111) at a photon energy of 5.2 eV are (3.5±1.2)×10−20 and (1.3±0.1)×10−19 cm2 , respectively.