Charge-state evolution of highly charged ions transmitted through microcapillaries

Abstract

The charge-state evolution of highly charged ions transmitted through microcapillaries is studied theoretically by a classical trajectory Monte Carlo simulation. The interaction of highly charged ions with the internal surface of the capillary is treated within the framework of dielectric response theory. We analyze the distance of closest approach and the angular distributions of the highly charged ions at the exit of the microcapillary. We find the charge-state fraction of transmitted N 61 projectiles, in good agreement with first measurements. Moreover, our calculations indicate that grazing collisions with the microcapillary surface hold the promise of direct observation of charge transfer and hollow-atom formation at a large distance from the surface. PACS number~s!: 34.50.Dy Collisions between highly charged ions ~HCI! and solid surfaces are currently at the center of numerous experiments and theoretical investigations @1‐8#. The main motivation of these efforts is the study of the fundamental interaction mechanism between the HCI and the solid surfaces. An accurate knowledge of these processes is very important for the use of HCI as a surface diagnostic tool as well as for surface modifications~see, e.g., @9#!. From a number of experimental and theoretical studies the following scenario of the HCI-surface interaction has emerged: When a highly charged ion approaches a solid surface, one or more electrons can be resonantly captured at a characteristic distance ( dc) into Rydberg states of the projectile with large principal quantum numbers nc . As a result, a multiply excited Rydberg atom with inner-shell vacancies, a