TUNNELING IN THE C2H-H2 REACTION AT LOW-TEMPERATURE

Low-temperature experiments on the ion-molecule reaction between NH3+ and H-2 show that this reaction can occur with an appreciable rate at very low temperature (much less than 100 K) despite the existence of an activation energy barrier. Theoretical calculations have confirmed the mechanism for the process at low temperature to involve tunneling. Although very-low-temperature neutral-neutral reactions between radicals and H-2 have yet to be studied in the laboratory, it is possible that such reactions can also proceed via tunneling under activation energy barriers. We estimate a non-negligible rate for the reaction between the radical CCH and H-2 at very low temperatures.