Electron capture by Ne²⁺ ions from atomic hydrogen

Using a merged-beam technique, the absolute, total electron-capture cross section has been measured for collisions of Ne²⁺ ions with hydrogen (deuterium) atoms at collision energies between 139 and 1490 eV/u. These data are compared to three other published measurements, two of which differ from one another by a factor greater than two. Early quantal rate coefficient calculations for Ne²⁺ ions with hydrogen at eV/u energies predict a cross section many orders of magnitude below the previously measured cross section at 40 eV/u. A possible explanation is given for the discrepancy between theory and experiment.