Temperature dependence of the three-body association of Cl−, NO−2, and NO−3 with SO2

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Abstract
The temperature dependence of the three body association reactions X−+SO2+He →X−SO2+He with X−=Cl−, NO−2, and NO−3 were studied at temperatures from 150 to 375 K in a flowing afterglow apparatus. The measured rate constants are given by the expressions k1=3.9×10−29 (300/T)2.1(±0.4) cm6 s−1, k2=2.4×10−28 (300/T)2.65(±0.2) cm6 s−1, k3=1.65×10−28 (300/T)3.75(±0.2) cm6 s−1. The increase of the rate constants with decreasing temperature are similar to those observed previously for positive ion association reactions with reactants of comparable complexity. The increase in the temperature coefficient with molecular complexity reflects the role of vibrational motion in the intermediate complex lifetime.