Concentration dependence of the spectroscopic and photochemical properties of atomic and molecular oxygen in argon matrices

Abstract

Vacuum ultraviolet (VUV) excitation (200–100 nm) and visible emission (300–650 nm) spectra of O 2 imbedded in Ar matrices at different concentrations are presented. At 0.1 and 0.2% concentrations a linear increase in the intensities of the excitation and emission spectra is observed. At these concentrations, photolysis of O 2 is found to be negligible. At higher concentrations (0.5, 1 and 2%) the normalized intensities of the excitation and emission spectra of O 2 decrease. With increasing concentration of O 2 the permanent photolysis of O 2 increases, which does not correlate, based on the excitation spectra of O in Ar, to the production of isolated O atoms. It has been shown that this anomalous behavior should be due to the formation of van der Waals dimers and oligomers at higher concentrations of O 2 that upon photolysis produce ozone.