Electron capture collisions between ${\mathrm{Na}}^{+}$ and ${\mathrm{O}}_2$, ${\mathrm{N}}_2$, and CO in the energy range 0.1-1 keV

Absolute cross sections for charge transfer into several excited levels of sodium have been determined over the energy range 0.1-1 keV. The energy dependence of all cross sections appears to follow the form $\sigma (v,\Delta E)=K{e}^{\frac{-\Delta \mathrm{Ea}}{\hslash v}}$, where $v$ is the ion velocity and $\Delta E(n,l)$ is the "energy defect" for charge transfer into $n$, $l$ excited levels of sodium. This experiment is the first test of the adiabatic hypothesis in which $v$ and $\Delta E$ can be treated in the above expression essentially as independent variables. We find that at constant $v$, relative magnitudes of electron-capture cross sections are governed by the energy defect without regard to principal quantum number or angular momentum of the final state. This functional dependence is discussed in terms of a semiclassical coupled harmonic oscillator model.