Excited state reaction dynamics of Ti(a⁵F(J)) + O₂ → TiO(A³Φ, B³Π, C³Δ) + O studied by a crossed-beam velocity map imaging technique.

Abstract

Oxidation reactions of the gas-phase titanium atom in its excited state with oxygen molecule, Ti(a(5)F(J)) + O2 → TiO(A(3)Φ, B(3)Π, C(3)Δ) + O, were studied by a crossed-beam velocity map imaging technique at 14.3 kJ/mol of collision energy. Metastable excited Ti, Ti(a(5)FJ), was generated by an optical pumping method and the reaction products were detected by single photon-ionization followed by a time-of-flight mass analysis and a two dimensional detection. Three wavelengths were selected to ionize electronically excited TiO*, TiO(A(3)Φ, B(3)Π, C(3)Δ). Time sliced images were measured, and angular and speed distributions of TiO* were determined. In all three ionization wavelengths, the angular distributions showed a forward-backward symmetry with low intensity at the sideway direction. The speed distributions were represented by the distributions based on the statistical energy partition into products. These results suggested that the reaction of Ti(a(5)F(J)) to form TiO(B) and TiO(C) proceeds via a long-lived intermediate and confirmed that the mechanism proposed by the previous chemiluminescence study.