Grazing incidence scattering of highly charged ions

Abstract

When a highly charged ion (HCI) impacts onto a surface, the HCI typically neutralizes within femtoseconds [1]. This is mostly attributed to surface-near processes such as Interatomic Coulombic Decay (ICD) [2], which depends strongly on the minimal distance dmin between ion and surface. In a grazing incidence scattering geometry, dmin can be tuned to a certain degree, potentially minimizing the effect of ICD. Past ex- periments with incidence angles of 1.2° < ωin < = 1.6° showed almost all outgoing particles to be neutral [3, 4]. At even smaller ωin, dmin sig- nificantly increases leading to a noticeable frac- tion of non-neutral projectiles despite the major- ity still neutralizing fully. We present here how projectile parameters (such as energy and ωin) influence the charge exchange and the resulting measured final charge state dis- tributions: Fig. 1 (a) shows the influence of ωin for Ar14+-ions with 62 keV kinetic energy im- pacting on a well-prepared Ni(110)-surface. As ωin gets more grazing, dmin gets larger which leads to overall fewer charge exchange. Panel (b) shows the influence of projectile energy for Ar10+-ions impacting on the same Ni(110) sur- face with ωin = 0.1°. Slower particles will experi- ence more charge exchange, leading to a smaller portion of non-neutral charge states. In this contribution, we present how other pa- rameters (such as projectile-target combination and charge state) influences the charge exchange. We will discuss the mechanisms involved in the de-excitation and present a model [5] to simulate and explain the observed phenomena. References [1] A. Niggas et al. Commun. Phys. 4 180 (2021) Figure 1: Charge state distributions after inter- action of Ar-ions being scattered from a well- prepared Ni (110)-single crystal. The distribu- tions are normalized to the intensity of the neu- tral particles. (a) shows the dependence on the angle of incidence ωin for Ar14+-ions with Ekin = 62 keV. (b) shows the dependence on the projec- tile kinetic energy for Ar10+-ions at ωin = 0.1°. [2] R.A. Wilhelm et al. Phys. Rev. Lett. 119 103401 (2017) [3] S.Wineckietal.Phys.Rev.A534228(1996) [4] N.Hatkeetal.Nucl.Instrum.MethodsPhys. B 115 165 (1996) [5] M. Werl et al. Phys. Rev. Res. 7 013176 (2025)