Dynamics of the Rydberg state population of slow highly charged ions impinging a solid surface at arbitrary collision geometry

Abstract

We consider the population dynamics of the intermediate Rydberg states of highly charged ionsinteracting with solid surfaces at arbitrary collision geometry. The recently developed resonant two-state vector model for the grazing incidence (2012 J. Phys. B: At. Mol. Opt. Phys. 45 215202) is extended to the quasi-resonant case and arbitrary angle of incidence. According to the model, the population probabilities depend both on the projectile parallel and perpendicular velocity components, in a complementary way. A cascade neutralization process for + Xe Z ions, for -= Z 15 45, interacting with a conductive-surface is considered by taking into account the population dynamics. For an arbitrary collision geometry and given range of ionic velocities, a micro-staircase model for the simultaneous calculation of the kinetic energy gain and the charge state of the ion in front of the surface is proposed. The relevance of the obtained results for the explanation of the formation of nanostructures on solid surfaces by slow highly charged ions for normal incidence geometry is briefly discussed.

Effect of the cascade neutralization energy on the surface modification by the impact of slow highly charged ions

“…The first state evolves from the initial state |Ψ 1 (t in ) (electron in metal) towards the future, and the second state evolves towards the fixed final state |Ψ 2 (t f in ) (electron captured by the ion). The states of the active electron at the time t (at ion-surface distance R) between the initial time t in and the final time t f in are expressed via intermediate eigenstates |µ M (R) and |ν A (R) of the in-HamiltonianĤ 1 (R) and the out-HamiltonianĤ 2 (R), respectively (Nedeljković et al, 2012;Nedeljković et al, 2016). By the ap-propriate expressions of the HamiltoniansĤ 1 (R) andĤ 2 (R) we take into account the polarization of the metal surface and the polarization of the ionic core, respectively, as well as the effect of the dielectric film (Majkić et al, 2017).…”

“…The effect of the arbitrary collision geometry is taken into account by the Galilean invariance, i.e. by the translation factor in the function |Ψ 2 (t) (Nedeljković et al, 2012;Nedeljković et al, 2016) expressed via perpendicular velocity component v ⊥ , and the energy shift…”

“…For very low ionic velocities the population process is resonant. In the more general velocity case, the intermediate population probability is given by (Nedeljković et al, 2016), where T ν A (t) is calculated by the integration of the transition probability density T µ M ,ν A (t) (Nedeljković et al, 2012):…”

“…All quantities in (2) are defined for the quasi-resonant electron transitions, i.e. at ion-surface distance R we have γ M = γ A (R); the influence of the energy levels with γ M γ A (R) is expressed via E (Nedeljković et al, 2016). The quantity f Ω k represents the angle-averaged Fermi-Dirac distribution of the electron momenta in solid (Nedeljković et al, 2012).…”

“…Detailed study of the interaction of slow highly charged ions (HCI) with solid surfaces is of great interest for the analysis of the surface modification by their individual impact (Nedeljković et al, 2016). Depending on the ionic velocity and on the type of the solid surface, different surface structures (features) can be created (Aumayr et al, 2011;El-Said et al, 2008.…”