Collision-induced emission of O 2 (a 1Δ g → X 3Σ g−) in the gas phase

Abstract

Emission of the 0–0 and 0–1 bands of the a 1Δ → X 3Σ g − system of molecular oxygen has been studied over the pressure range 0.5–25 Torr in a flow system using a Fourier-transform spectrometer. At high oxygen pressures and on the addition of NO, continuous emissions of O 2(a): M collision complexes were found to appear in both bands beneath the discrete rotational lines of the magnetic dipole transitions. In both cases, the continua are distinctly broader than the unresolved low-pressure a → X bands. In the presence of Ar, Kr, Xe, N 2, CO 2 and SF 6 narrower continua were found, but only in the 0–0 band. Bimolecular rate constants for the collision-induced emission processes were derived from the ratios of the intensities of the continua and of the discrete lines. For O 2 as collision partner, the rate constants at 298 K for the 0–0 and 0–1 bands were found to be (3.4 ± 0.3) × 10 −23 and (1.4 ± 0.1) × 10 −23 cm 3 s −1, while for NO they were (1.72 ± 0.03) × 10 −21 and (9.2 + - 0.7) × 10 −23 cm 3 s −1.