The ion fractions of 2–10 keV lithium, sodium and potassium scattered from a copper (100) surface

Abstract

The ion fractions of lithium, sodium and potassium scattered from a copper (100) surface have been measured as a function of several experimental parameters. The ion fraction appears to be almost independent of the final energy, i.e. independent of the type of scattering trajectory at or below the surface. This means that the alkali ions can be used very well in several cases when experimental data are to be compared with theoretical scattering models. Typical values of the ion fraction are: 63% for lithium, 76% for sodium and 99% for potassium (values are given for a primary energy of 5 keV). A comparison of the results has been made with a theory based on ideas developed for the adsorption and scattering of very low energy alkali particles. A qualitative agreement has been found for the dependence of the ion fraction on the ionization energy of the alkali atoms and the (slight) variation with the primary energy.