Temperature and pressure dependence of the reaction of He+ ions with H2

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Abstract
The reaction of He+ ions with H2 has been studied in the temperature range from 18 to 408 K using a selected‐ion drift‐tube apparatus. The reaction rate coefficients are very small and do not exceed 2×10−13 cm3 s−1 at low pressure in the whole temperature range. The rate coefficients are pressure dependent. This indicates that a two‐body and a three‐body collision process contributes to the observed reaction rate. The three‐body reaction rate coefficient is steadily increasing with decreasing temperature, approximately k3=1.6×10−30(100/T)1.27. To explain the three‐body reaction process it has to be assumed that an intermediate complex He+–H2 with a lifetime of just a few vibrational periods exists.