Collisional excitations in quasi two-electron systems: Mg-He, Ne, Ar and Li, K-Na

Abstract

The authors present an investigation of collisional excitations in systems characterised by the presence of two valence electrons localised outside closed shells in the energy range 1-300 keV. Two types of systems have been studied: (i) systems such as Mg-rare gases with both valence electrons localised on the projectile, and (ii) systems such as Li, K-Na with one valence electron localised on the projectile and one on the target. Experimentally, the total emission cross sections and polarisations have been measured for the Mg I 31S-31P, 33P-43S, s3P-33D, 33P-3p2 3P, Li I 22S-22P, Na I 32S-32P and K I 42S-42P transitions. The content metastable Mg(3s3p3P) atoms in the applied neutral Mg beams has been determined by means of an optical method based on the Wigner spin conservation rule in low-energy atomic collisions. The Mg(3s2)-He collision has been examined theoretically using a Hartree-Fock frozen-core potential to describe the interaction between the Mg valence electrons and the He atom.