Single Electron Capture in Slow Collisions of Doubly Charged Ions with Dinuclear Molecules

Mihaela Albu,Hannspeter Winter,Friedrich Aumayr,Libor Mrazek

doi:10.3390/i3030209

Abstract

We have performed translational-spectroscopical measurements on single electron capture (SEC) by impact of slow (impact energy ≤ 1 keV) doubly charged ions on dinuclear molecules. For impact of C2+ and N2+ ions the influence of their metastable fractions on the SEC probability has been studied. For impact of 4He2+ on O2 and CO direct and dissociative SEC have been investigated. For all collision systems studied the principal SEC channels can be explained by the "reaction window" which results from multichannel-Landau-Zener treatments for the collisional quasimolecules.

Highlights

Collisions of slow doubly charged ions with simple molecules are of interest in hot thin plasmas for various fields, in particular ionospheric physics, plasma technology and thermonuclear fusion
By means of the translational attenuation method, a priori unknown metastable doubly-charged primary ion beam fractions can be characterized for subsequent single electron capture (SEC) reactions
The method utilizes the strong selectivity of SEC at low impact energies in suitably chosen attenuation gases, which causes preferential attenuation of either ground state- or metastable doubly charged ions before entering the translational energy spectrometer

Summary

Introduction

Collisions of slow doubly charged ions with simple molecules are of interest in hot thin plasmas for various fields, in particular ionospheric physics, plasma technology and thermonuclear fusion. Sci. 2002, 3 energy of 3.5 MeV in series of elastic collisions to the deuterium and tritium fuel ions, and after having slowed-down end up as "He ash" The latter must be efficiently removed from the plasma in order to avoid inacceptable bremsstrahlung loss and fusion fuel dilution. In collisions of doubly charged ions with neutral molecules single electron capture (SEC) is a highly probable process which can produce molecular ions in both bound and unbound (dissociated) states, depending on the given internal energy. The obtained translational energy spectra (TES) showed that both 2s2 1S ground state- and 2s2p 3Po metastable C2+ ions can give rise to important SEC channels if the corresponding reaction energy defects fall into the socalled "reaction window" (moderately exothermic reactions with about 3 ≤ ∆E ≤ 6 eV (∆E is the respective kinetic energy gain). By means of a differentially-pumped charge-exchange cell in front of the translational energy spectrometer the primary-ion beam composition can be varied (see below)

Discussion of experimental results

Summary and outlook