The Mobility of H+3 and H+5 Ions in Hydrogen and the Equilibrium Constant for the Reaction H+3+2H2<=> H+5+H2 at Gas Temperatures of 195, 273 and 293 K

The mobilities of hydrogen ions in hydrogen have been measured by the Bradbury-Nielsen time-offlight method at temperatures of 195, 273 and 293 K, at pressures in the range O' 5-200 torr and at E/ N values ranging from 0�4 to 200 Td. The zero field reduced mobilities of H~ and H~ have been determined to be 1l�18�0�05 and 10'61�0'05cm2 s-1 V-1 at 293K, and 1l�18�0�05 and 10'53�0'05cm2 s-1V-1 at 273�2K respectively. At 194'5K the zero field reduced mobility of H~ was determined to be 10�40�0�05 cm2 s-1V-1 ? The thermal equilibrium constant K. for the reaction H~ + H2 + H2 +2 H~ + H2 was obtained by fitting the mobility data as a function of gas pressure. The values of K. obtained were 1�83�0�45 X 10-18, 2�8�0�7 X 10-18 and 1'6�0'6 x 10-16 cm3 at 293,273 and 195 K respectively. The reduced mobility of Hj as a function of E/N was derived for values of E/ N up to 200 Td from the data taken at gas pressures less than 2 torr and was found to be in good agreement with the data of Miller et al. (1968). The ion species present were identified by the addition of contaminants and by use of supplementary data taken with a drifttube- mass-spectrometer system. The energy for the dissociation of H~ into Hj and H2 was derived by the method of Eyring et al. (1936) and found to be 250� 50 meV.