Elastic Scattering of Beryllium Doubly Charged Ions in Helium

The scattering of ${\mathrm{Be}}^{++}$ ions of energy 100-800 eV by He has been measured by observing the energy-loss spectrum of the ions on traversing various path lengths of the scattering gas. The scattering data have been analyzed to determine an interaction energy for ${\mathrm{Be}}^{++}$ and He for the internuclear separations from 0.15 to 1.0 Å. While not strictly logarithmic, the results can be approximately fitted by an expression for the interaction which is $V\left(r\right)=6.0\mathrm{}\times {10}^2\times e^{-5.70r}$ eV, with $r$ in Å. A Thomas-Fermi-Dirac calculation of the interaction energy fits the experimental result well for $r>\mathrm{}0.3\mathrm{}$ Å.