The Journal of Chemical Physics · 1990 · 66 citations · 19 references
Natural SciencesChemistryPhysicsAtmospheric ChemistryPhysical ChemistrySpectroscopyFluorescence SpectroscopyLaser PhysicsLaser SpectroscopyLaser-plasma InteractionsMolecular CollisionsRotational SpectroscopyAtmospheric Pressure DependenceCollision Cross SectionsExcited State QuenchingFluorescence QuenchingLaser-induced FluorescencePressure DependenceQuenching ProcessesRotational Level Populations
Collisional quenching of the v′=0 level of the A 2Σ+ state of the OH molecule has been studied for a variety of collision partners. The pressure dependence of time-resolved, laser-induced fluorescence furnishes the quenching cross sections σQ. OH radicals are produced in a microwave discharge or by photolysis of HNO3 at 193 nm, always in sufficient Ar bath to produce a thermal rotational population at 300K in the laser-excited A 2Σ+ state. For Kr and Xe, the σQ are 8 and 27 Å 2, respectively; comparison with a prior study suggests a decrease in σQ with increasing rotational level and/or increasing temperature. σQ (O2)=18 Å 2,and σQ (H2O)=80 Å 2; cross sections were measured for selected freons and butanes also important in tropospheric laser measurements of OH.
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