The cross section for symmetric charge exchange of Ne+in Ne and Ar+in Ar at low energies

The mobilities of Ne + in Ne and Ar + in Ar have been measured at 293 K at E/N values up to 1000 Td using a variable length drift tube employing Tyndall-Powell grids. Measurements were also made of the mobility of Ar + in Ar at 216K over the range 100-500 Td. The room temperature data were used to obtain the charge exchange cross section over the energy ranges 0.12-1.25 eV (lab) for Ne + in Ne and 0.11 to 0.63 (lab) for Ar + in Ar with an uncertainty of less than +or-5%. Before use in the analysis the data were corrected for the effect of thermal motion by using a relation based on the work of Forsth and Skullerud (1979). The accuracy of this procedure was checked by comparing the predicted and experimental values at 216K and also by a Monte-Carlo calculation. Sources of error in the analysis are discussed and the derived cross sections compared with previous results.