Quenching of laser-excited O2(b 1Σ+g) by CO2, H2O, and I2

Abstract

The total quenching rates of O₂(b ¹Σ⁺_g) by CO₂, H₂O, and I₂ have been determined to be (4.53±0.29)×10⁻¹³ cm³ molec⁻¹ sec⁻¹, (6.71±0.53)×10⁻¹² cm³ molec⁻¹ sec⁻¹, and (2.04±0.28)×10⁻¹¹ cm³ molec⁻¹ sec⁻¹, respectively. A pulsed, Raman‐shifted dye laser was used to excite a single rotational line of O₂(¹Σ, v′=0), while subsequent ¹Σ→³Σ fluorescence was monitored by a photon counting technique to determine the deactivation rate as a function of the partial pressure of quenching gas. Rate constants for deactivation of O₂(¹Σ) by CO₂ and H₂O were found to be consistent with those measured elsewhere, whereas I₂ was found to quench O₂(¹Σ) an order of magnitude more slowly than reported in the literature. The lower total quenching constant for I₂ suggests that the reaction O₂(¹Σ)+I₂→O₂(³Σ) +2I might not be responsible for dissociation of I₂ in the chemical oxygen‐iodine laser.