The bimolecular reaction of C2H+2 with H2 is found to undergo a surprising change of mechanism to one of inverse energy dependence below temperatures of 3 K as observed in a free jet flow reactor. The observed rate coefficient for C2H+3 production is found to be k=5.6×10−11 T−2 cm3/s in this energy regime. Contrary to previous belief, the reaction is exothermic and results are described regarding kinetic isotope effects, the competitive three body association process and internal C2H+2 vibrational state dependency of the chemistry. A mechanism is suggested which involves a low temperature switching to a tunneling process through a small barrier and is intimately coupled to the long lived complex properties of very low energy collisions.
The gas phase reaction of C2H+2 with H2 below 3 K: The reopening of the bimolecular C2H+3 channel at low energy
Michael Hawley, Mark A. Smith; The gas phase reaction of C2H+2 with H2 below 3 K: The reopening of the bimolecular C2H+3 channel at low energy. J. Chem. Phys. 15 January 1992; 96 (2): 1121–1127. https://doi.org/10.1063/1.462198
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