Collisional quenching of OH(A 2Σ+, v′=0) by H2O between 211 and 294 K and the development of a unified model for quenching

The cross-section for electronic quenching of OH(A 2Σ+, v′=0) by H2O was found to increase from 82±8 Å2 at 294 K to 119±11 Å2 at 211 K. Both OH(A 2Σ+) and H2O display relatively large dipole moments, and a `harpoonedʹ mechanism occurring on a Lennard-Jones potential energy surface modified to include dipole moment effects was found to reproduce the observed temperature dependence of the cross-sections in the range 211–2300 K. The model, which is general, will enable corrections for the effects of quenching on laser-induced fluorescence signals to be made with a high degree of confidence in combustion and atmospheric media.