Rates of collision-induced emission from metastable O(1<i>S</i>) atoms

Abstract

The radiative decay of metastable 1s22s22p4 1S0 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.