A measurement of the vibrational band strength for the ν3 band of the HO2 radical

Abstract
The HO2 radicals generated in a discharge‐flow system have been observed with tunable diode laser absorption in the P branch of the ν3 vibrational band at 1080 cm1. The observed line positions agree within (2 to 5)×103 cm1 with those calculated from the molecular constants for the ν3 band obtained from a previous study using laser magnetic resonance spectroscopy. The band strength has been determined by observing line center absorptions when HO2 is produced in the reaction F+H2O2→HO2+HF (k1) with a measured concentration of atomic fluorine and excess hydrogen peroxide. F‐atom concentrations are measured by diode laser absorption of the spin‐orbit transition at 404 cm1. The analysis accounts for HO2 losses due to the reactions of HO2+HO2→H2O2+O2 (k3) and F+HO2→HF+O2 (k4). The experimental data are consistent with a value of k3=(1.6±0.3)×1012 cm3 s1 and a ratio k4/k1=1.0±0.4. The line strength for the 615←716 F1 transition is 2.9×1021 cm2 molecule1 cm1 which corresponds to a ν3 band strength of 35±9 cm2 (STP atm)1. This value is a factor of 1.6 to 6 lower than previous ab initio calculations.

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