Charge Transfer between Alkali-Metal Ions and Cesium Atoms

The cross sections for charge transfer between alkali-metal ions and cesium atoms have been determined as a function of primary ion beam energy from 50 to 4500 eV. In all cases, structure consisting of oscillations whose amplitudes increased with primary ion beam energy was observed superimposed upon the normally expected form of the cross sections. Smith has shown that the cesium resonance results follow from the assumption that the difference between the even and odd eigenenergies ($V_g-V_u$) passes through an extremum. We find that the resonant cross section can be described by $Q\left({\mathrm{cm}}^2\right)=Q_0\left({\mathrm{cm}}^2\right)-A{V}^{\frac{1}{4}}cos\left[\pi \mathrm{}\right(\left|B\right|V^{\frac{-1\mathrm{}}{2}}-\frac{1}{4}\left)\right]$ where $A=0.75\mathrm{}\times {10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$ e${\mathrm{V}}^{-1/4\mathrm{}}$, $B=-820\mathrm{}$ e${\mathrm{V}}^{1/2}$, $V$ is the ion beam energy, and $Q_0$ is the nonoscillating portion of the cross section. This expression results from the assumption that $V_g-V_u$ passes through a minimum of a negative function of internuclear distance. Potential parameters consistent with the quoted values of $A$ and $B$ are given. The nonresonant results can be fitted by the form $Q=Q_0-A{V}^{\frac{1}{4}}cos\left[\pi \mathrm{}\right(\left|B\right|V^{\frac{-1\mathrm{}}{2}}+\frac{1}{4}\left)\right]$.