The formation and destruction of highly excited helium atoms in 4–25 keV collisions with the rare gases and simple molecules

Abstract

The production of highly excited (10 < n < 20) helium atoms has been investigated in 4–25 keV He + collisions with the inert gases, hydrogen and nitrogen using the field ionization technique. Cross-sections are found to scale as n −3, and in the case of heavier rare gases there are signs of structure at low energies. The destruction of highly excited (10 < n < 20) helium atoms in collisions with N 2, He, Ar and Xe has been investigated within the same energy range. Cross-sections are in good accord with the independent particle model, in which the core and excited electron scatter quasi-freely.