We have investigated the intermediate stages of electron capture into Rydberg states of multiply charged ions ͑core charge Z 1, principal quantum number n A 1͒ escaping solid surfaces at low velocity. The timesymmetrized, two-state vector model of the process is proposed by using both initial and final states of the ion-surface system. The two conditions determine two wave functions and both are used to describe the system at intermediate stages. The appropriate probabilities and rates are defined and calculated from the corresponding mixed flux. Taking into account both the surface polarization and the polarization of the electronic cloud of the ionic core, the probabilities and rates are obtained in a simple analytical form; the population of the Rydberg levels of the ions Ar VIII, Kr VIII, and Xe VIII interacting with an Al surface is considered as an example. The quasiresonant character of the process is demonstrated, as well as the complementarity of the neutralization and ionization processes for the A Z+ ions escaping the surface and the A ͑Z−1͒+ ions approaching the surface, respectively. The neutralization distances for the ions finally detected in a given Rydberg state are obtained from the calculated rates. Although defined under different physical conditions, the results obtained are in agreement with the coupled-angular-mode theoretical predictions.

We elaborate the quantum-mechanical analysis using the two-state vector model to investigate the formation of intermediate Rydberg states of multiply charged ions (core charge Z ≫ 1, principal quantum number nA ≫ 1) interacting with solid surfaces in the grazing incidence geometry. For the fixed initial and final states of the active electron, the two wavefunctions are used to describe the transitional electron state at the time t. Considering the projectile motion classically, the effect of projectile velocity is taken into account in accordance with Galilean invariance. The population probabilities of the intermediate Rydberg states are obtained in the analytical form, which enables an analysis of the localization and the selectivity of the process, for various ion–surface parameters. Ions ArZ+, KrZ+ and XeZ+ with Z ∈ [5, 35] interacting with Al-surface are considered as an example. The results are compared with the classical overbarrier predictions and the measured kinetic energy gain due to the image acceleration of the ions. It is demonstrated that the ionic velocity influences the ion–surface distance at which the formation of the particular intermediate Rydberg state is mainly localized, as well as the probability for this formation.

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