Rates of collision-induced emission from metastable O(1S) atoms

Abstract

The radiative decay of metastable 1s²2s²2p^{4 1}S₀ atomic oxygen atoms has been shown to proceed at a rate depending linearly on the concentration of argon or xenon present in the gas mixture. With increasing pressure, the ¹D₂–¹S₀ atomic line at 5577 Å becomes accompanied by a broad emission region identified as a band system of a weakly bound rare‐gas oxide molecule. Changes in the transition probability as a function of pressure were measured by using the spin‐forbidden ³P₁–¹S₀ transition at 2972 Å as a pressure‐independent monitor of the O(¹S) concentration. The observed pressure dependence of the emission probability may be described by rate constants for induced emission in argon and xenon atmospheres: (1) for emission in a bandwidth of ±1.6 Å centered on the atomic line at 5577 Å, k(Ar)=(7±3)×10⁻²⁰ cm³ sec⁻¹, k(Xe)=(3±2)×10⁻¹⁹ cm³ sec⁻¹; and (2) for emission into the entire green band system, k(Ar)=(3.0±.2)×10⁻¹⁸ cm³ sec⁻¹, k(Xe)=(1.7±.2)×10⁻¹⁵ cm³ sec⁻¹. Comparison is made with rate constants for deactivation of these metastable atoms by the same rare gases. It appears that substantially all of the collision‐induced emission comes from bound rare‐gas oxide molecules whose dissociation equilibria provide the observed pressure dependence.