| Abstract
| - Ion−molecule reactions involving metallic species play a central role in the chemistry of planetary ionospheresand in many combustion processes. The kinetics of the Ca+ + N2O → CaO+ + N2 reaction was studied bythe pulsed multiphoton dissociation at 193 nm of organo-calcium vapor in the presence of N2O, followed bytime-resolved laser-induced fluorescence spectroscopy of Ca+ at 393.37 nm (42P3/2 ← 42S1/2). This yieldedk(188−1207 K) = 5.45 × 10-11 (T/300 K)0.53 exp(282 K/T) cm3 molecule-1 s-1, with an estimated accuracyof ±13% (188−600 K) and ±27% (600−1207 K). The temperature dependence of this barrierless reaction,with a minimum in the rate coefficient between 400 and 600 K, appears to be explained by the role of N2Ovibrational excitation. This is examined using a classical trajectory treatment on a potential energy surfacecalculated at the B3LYP/6-311+g(2d,p) level of theory.
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