Collisional Deactivation of O₂(¹Σ_g⁺) by Small Polyatomic Molecules

Abstract

Literature data on the collisional deactivation of O2(1Σg+) by small polyatomic molecules in the gas phase are interpreted by a deactivation model which has proven to describe successfully the experimental findings for the collisional deactivation of O2(1Δg) in the liquid phase. Deactivation occurs by electronic to vibrational energy transfer from the excited O2 molecule to peripheral bonds X—Y of the quenching molecule. Using data on Franck‐Condon factors and transition energies for the possible coupled transitions O2(1Σg+, ν = 0 → 1Δg, ν = m) and X—Y (ν' = 0 → ν' = n) experimental rate constants kXYΣ of O2(1Σg+) quenching by X—Y can quite well be reproduced by calculated ones. The only parameter of the model which has to be changed is related with the electronic factor f of the corresponding O2 transition. As ratio of electronic factors of the 1Δg → 1Σg+ singlet‐triplet and 1Σg+ → 1Δg singlet‐singlet transitions fST/fSS = 6 · 10−5 is obtained. Independent measurements of radiative lifetimes of these transitions in an Ar‐matrix yield fST/fSS = 9 · 10−5 confirming our results. Thus for the first time collisional deactivation of O2(1Δg) and O2(1Σg+) by small polyatomic molecules is explained consistently.