Excitation of Ne, Ar, Kr and Xe by He + impact (0.3–10 keV)

Abstract

Impact radiation from He + in Ne, Ar, Kr and Xe is studied in the wavelength region between 500 Å and 2000 Å. This work forms a continuation of the measurements between 3000 Å and 6000 Å, which have been published in a preceding article. There we have discussed the relatively strong production of spectral ion lines of the target atom, whose emission cross sections in many cases show a striking increase with decrease in impact energy. The deviation from the normal adiabatic behaviour in the lower energy range was explained by the effect of pseudo-crossing of the potential curves of the collision complexes before and after the reaction. In the present experiment the same behaviour is found for many ion spectral lines in the vacuum ultraviolet region. The experimental results indicate that the upper levels of these spectral lines are populated not only by the collision process, but for a large part via cascade from higher excited ion levels formed in the collision process. There is strong evidence that in the low-energy region (∼300eV) most of the electron capture processes go in combination with the formation of the excited ion states of the target atom, considered in this article. Further we find that the deviation from the normal adiabatic behaviour is not only confined to the emission of the ion spectral lines, but also occurs for atomic spectral lines of the target atom.