Anisotropic excitation of argon ion excited states by grazing collisions with metal and carbon surfaces

Abstract

The relative Stokes parameters of transitions from excited states of 40–100 keV Ar + ions have been measured following grazing collisions with copper, stainless steel, and carbon targets. The states were formed by the capture of an l=1 electron to a common 3P parent state. The relative orientation and alignment irreducible tensor parameters of the excited states were derived from the data as a function of ion velocity using the isotropic core model. The relative orientation parameter, which tended to increase linearly with ion velocity, was very similar for copper and stainless steel, but lower in magnitude for a carbon surface. Orientation of the 4 p 4 S° 3 2 level indicates a partial failure of the isotropic core model. Interesting effects of polarization due to adsorbates were also observed. The data are discussed in terms of the density gradient model, with electron capture from localized and band states.