The generalized mobility curve for alkali ions in rare gases: Clustering reactions and mobility curves

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Abstract
The measurements of mobility values for alkali ions in rare gases at room temperature over a wide range of E/N were completed for all 25 combinations. The experimental mobility curves were compared with a generalized mobility curve calculated from a model potential consisting of an inverse 8th power repulsive term and 6th and 4th power attractive terms, which took into account the core size, and potential well depths being determined for all the ion–gas combinations except for the cases of Rb+–He and Cs+–He from the relation between the observed maximum mobility and the ion energy. Experimental generalized mobility curves for alkali ions in rare gases were obtained using these well depths. It was found that all the experimental mobility curves were unified into a single curve using the model potential including the core size. The rate coefficients were measured for backward clustering reaction: Li+Ar–Ar, Li+Kr–Kr, and Li+Xe–Xe, using a drift tube. It was found that the activation energy is roughly half the well depth, comparing the well depths 0.550 eV for Li+–Ar, 0.710 eV for Li+–Kr, and 0.901 eV for Li+–Xe, with the activation energies obtained by Arrhenius plot for the backward reactions 0.34 eV for Li+Ar, 0.45 eV for Li+Kr, and 0.49 eV for Li+Xe.