Electron-Induced Synthesis of Ozone in a Dioxygen Matrix

Ozone (${\mathrm{O}}_3$) was synthesized in the condensed phase induced by electron bombardment of multilayer films of molecular oxygen condensed at temperatures below 30 K on metal surfaces. ${\mathrm{O}}_3$ formation was demonstrated by the observation of the asymmetric stretching ( ${\nu }_3$) and bending ( ${\nu }_2$) normal modes of vibration in a high-resolution electron energy-loss spectroscopy experiment, and by characteristic changes in electron-stimulated desorption of ${\mathrm{O}}^{-}$. The threshold electron energy for the ${\mathrm{O}}_3$ formation is found at $3.5\pm 0.2\mathrm{eV}$. It corresponds to the formation of O${(}^3$P) associated with ${\mathrm{O}}^{-}\left({}_{}{}^2{}_{}{}^{}P\right)$ by dissociative electron attachment at condensed ${\mathrm{O}}_2$, followed by the third body reaction $\mathrm{O}+{\mathrm{O}}_2+{\mathrm{O}}_2\to {\mathrm{O}}_3+{\mathrm{O}}_2$. Above 5.1 eV bombarding energy, dissociative excitation of the ${\mathrm{O}}_2^{*}$ ( $c^1{\Sigma }_u^{-}{,C}^3{\Delta }_u{,A}^3{\Sigma }_u^{+}{,B}^3{\Sigma }_u^{-}$) states is the main source of atomic oxygen O${(}^3$P) or O${(}^1$D) involved in the ${\mathrm{O}}_3$ synthesis.