The role of near resonance electronic energy transfer on the collisional quenching of NO (A(2)Sigma(+)) by C6H6 and C6F6 at low temperature
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2017 Elsevier B.V. We present measurements of the collisional fluorescence quenching cross section of NO (A2+) by benzene and hexafluorobenzene at a series of temperatures using a custom built slow flow cell and a pulsed de Laval nozzle test cell. The measurements show a deviation from the common harpoon mechanism of collisional fluorescence quenching, specifically the large quenching cross section of 147 2 at 300 K measured for benzene which is not predicted by the harpoon mechanism due to the low electron affinity of benzene (1.5 eV). We speculate that the quenching of NO (A2+) by benzene and hexafluorobenzene occurs through near resonance electronic energy transfer from the NO A-state to the A-state of the quencher via a pseudo-emission process. The predicted T1/3 dependence of the cross section for this model is consistent with the experimental observations.