a Study of Quasi-One Systems: Excitation of the Active Electron to its First Excited State

Experimental angular differential cross sections (ADCS) of four Quasi-One-Electron (QOE) scattering systems (Li('+), Na('+) + H and Be('+), Mg('+) + He) are reported. These ADCS are determined for exciting the 'active' electron to its first excited state. The angular range of the ADCS is from 0 to (TURN)3 mrad(,lab) with an angular resolution of (TURN)120 (mu)rad(,lab). The energy range is from 19.4 to 150 keV with an energy-loss resolution of (TURN)1 eV. The ADCS are compared to the available theories. The agreement between experiment and theory ranges from very poor to fair. No experiments exist which allow direct comparison to the present results. Integration of the present ADCS gives results which are compared to the experimental and theoretical total He targets cross section results. The agreement changes from energy to energy. Theoretical total cross section results exist in the cases involving H targets and are in very poor to fair agreement with the present results. No experimental total cross sections exist in the H target case for comparison with the present results. The most striking feature occurs in the Na('+) + H ADCS. Here the value of the ADCS at zero angle changes by 2 1/2 orders of magnitude from (3.96 (+OR-) 2.00) x 10('-15) cm('2)/sr at 35.9 keV (v = 1/4 a.u.) to (1.03 (+OR-) 0.25) x 10('-12) cm('2)/sr at 143.8 keV (v = 1/2 a.u.). This steep rise in the ADCS at zero angle is interpreted as showing the onset of a direct excitation mechanism (mechanism ii in the QOE literature). Qualitative agreement between previous QOE results (at lower energy using He targets) and the present Na('+) + H results is shown. Massey parameter scaling is shown to supply relatively little information on the ADCS. Finally, the results are probed to show the similarities of the underlying scattering mechanisms. For systems with the same target, the ADCS show quantitatively comparable results implying considerable similarities. Although all the systems are shown to be qualitatively similar with respect to their underlying mechanisms, no quantitative comparisons are possible between scattering systems of differing targets.