Electron capture into large-lRydberg states of multiply charged ions escaping from solid surfaces

Abstract

We have investigated the electron capture into large-$l$ Rydberg states of multiply charged ionic projectiles (e.g., the core charges $Z=6,$ 7, and 8) escaping solid surfaces with intermediate velocities $(v\ensuremath{\approx}1\mathrm{a}.\mathrm{u}.)$ in the normal emergence geometry. A model of the nonresonant electron capture from the solid conduction band into the moving large angular-momentum Rydberg states of the ions is developed through a generalization of our results obtained previously for the low-$l$ cases $(l=0,$ 1, and 2). The model is based on the two-wave-function dynamics of the Demkov-Ostrovskii type. The electron exchange process is described by a mixed flux through a moving plane (``Firsov plane''), placed between the solid surface and the ionic projectile. Due to low eccentricities of the large-$l$ Rydberg systems, the mixed flux must be evaluated through the whole Firsov plane. It is for this purpose that a suitable asymptotic method is developed. For intermediate ionic velocities and for all relevant values of the principal quantum number $n\ensuremath{\approx}Z,$ the population probability ${P}_{\mathrm{nl}}$ is obtained as a nonlinear l distribution. The theoretical predictions concerning the ions S VI, Cl VII, and Ar VIII are compared with the available results of the beam-foil experiments.