Collisional transfer between and quenching of the 3p 3P and 5P states of the oxygen atom

Collisional quenching and excitation transfer between the oxygen atom 3p 3P and 5P states have been investigated in a discharge flow apparatus with O2 and N2 collisional partners. The 3P state was excited by two-photon excitation at 225.6 nm from the 2p43P ground state, and temporal profiles of the 3P←3S and 5P← 5S emission at 844.7 and 777.5 nm, respectively, to the lower 3s manifold were recorded. From an analysis of 3P decay curves as a function of quencher pressure, bimolecular rate constants for the removal of the 3P state were determined: k3Q(O2) = (7.8±0.8) × 10−10 and k3Q(N2)= (5.87±0.15)× 10−10 molecule−1 cm3 s−1. The intercept of the O2 Stern-Volmer plot yielded k3r = (2.98± 0.15)×10 7 s−1 for the 3P radiative decay rate. The collisional quenching rate constant for the 5P state by O2 was obtained by analysis of 5P decay curves: k5Q(O2)= (10.8±1.8)× 10−10 molecule−1 cm3 s−1. Rate constants k35 for 3P← 5P excitation transfer were obtained from the ratio of the 5P←5S to 3P← 3S emission intensities as a function of quencher pressure: k35 (O2) ≈ 6× 10−11 and k35 (N2)≈2 ×10 −11 molecule−1 cm3 s−1.