Multiple electron capture by highly charged ions at keV energies

Abstract

The status of the knowledge on the mechanisms of multiple captures by a highly charged ion colliding with an atom is reviewed. The various and complementary techniques are first described, including energy gain spectroscopy, electron and photon spectroscopy with a particular emphasis on the rapidly developing techniques combining these spectroscopies in coincidence experiments. The double capture processes are simple enough to allow theoretical calculations and a detailed analysis of capture mechanisms such as the relative role of the electron-nucleus interaction and the electron-electron interaction. This is not yet the case for multiple captures, which imply a very large number of channels. However the simple classical overbarrier model, in its extended form, is able to account for the gross features of multiple capture processes such as the number of electrons stripped from the target.

Electron Capture in Collisions of Slow Highly Charged Ions with an Atom and a Molecule: Processes and Fragmentation Dynamics

“…In parallel, theoretical methods, such as the classical overbarrier (COB) model [8], the Landau-Zener model [9], the classical trajectory Monte Carlo (CTMC) model [10], and molecular expansion close-coupling methods [11] have been developed. From such experimental and theoretical works, the main features have been explained successfully over a wide range of impact velocities [1,12].…”

“…However, even in the case of collisions involving only two active electrons, the processes responsible for DEC are still under debate [12,[18][19][20][21]. While DEC can be rather well described using independent electron models, it has been shown that dynamic correlation effects due to the electronelectron interaction which is not incorporated in these models may play a decisive role during the collision [22,23].…”

The relativistic operator of interaction of two quasimolecular electrons as a third-order effect of quantum electrodynamics

“…But at heat-scale collision energies, two-electron processes with rearrangement [3]- [7] become equally probable or even sometimes prevail over one-electron processes. These two-electron processes include various Auger processes [7], the two-electron charge exchange processes [3]- [6], and the charge exchange with simultaneous ion excitation [4]. Because the total cross sections and rate constants of these processes are large, we can assume that these processes with rearrangement are governed by electron transitions at relatively large distances R between colliding particles.…”

“…The presence of the small parameter 1/R allows developing a consistent asymptotic theory of the process under investigation. This is why several "memorable" results in the theory of multielectron atom-ion processes with rearrangement were obtained in the framework of the asymptotic approach [3], [4], [6]. * Uzhgorod National University, Uzhgorod, Ukraine, e-mail: lazur@univ.uzhgorod.ua, o.pavlik75@mail.ru, reiti@univ.uzhgorod.ua.…”

“…The interest in these problems is due to the possibility of laser radiation stimulation of various processes occurring in ion-atom collisions and involving electrons of both the outer and the inner electron shells. Most theoretical and experimental papers dealt with two-electron processes with rearrangement (see, e.g., [2], [6], [8]- [12] and the references therein), which occurs at large internuclear distances and are accompanied by absorption (emission) of photons. These processes include strongly correlated electronic transitions recently intensively studied both experimentally [2], [10] and theoretically [8], [11].…”