Resonances in the final Rydberg state population of multiply charged ions ArVIII, KrVIII, and XeVIII escaping solid surfaces

Abstract

The appearance of resonances (pronounced maxima at nA = n res) in the probability distributions for the population of the Rydberg state (nA, lA, mA) of multiply charged ions (Z ≫ 1) escaping solid surfaces at intermediate velocities (v ≈ 1 a.u.) is discussed. Within the framework of the time-symmetrized two-state vector model, in which the state of a single active electron is described by two wave functions Ψ1 and Ψ2, the resonances are explained by means of an electron tunneling in the very vicinity of the ion-surface potential barrier top. To include this specific feature of electron transitions into the model, the appropriate etalon equation method is used in the calculation of the function Ψ1. We consider the ions ArVIII, KrVIII, and XeVIII with the same core charges Z = 8 a.u., but with different core polarizations. The effect of the ionic core polarization is associated with the function Ψ2. The population probabilities for nA ≈ nres are complemental to those obtained recently for n A < nres, and in sufficiently good agreement with available beam-foil experimental data. The pronounced resonances in the final population distributions are recognized only in the case of ArVIII ion and for the lower values of the solid work function (argon anomaly). © 2011 Elsevier B.V. All rights reserved.