Two and three electron auger transitions in collisions of highly-charged ions with surfaces

Collective relaxation processes in atoms, molecules and clusters

“…Assuming that the lifetime of the double L-vacancy state with respect to the two-electron L−M M transition is comparable to that of the single vacancy state (i.e., 10 −14 − 10 −15 s), the CAD lifetime can be estimated as 10 −10 − 10 −12 s. In the same group, KK − LLL CAD of double core hole states of C and N was observed in analogous ion-atom collision experiment [84]. The measurement yielded comparable relative CAD intensities, namely 2.2 × 10 −4 for C and 3.1 × 10 −4 for N. The KK − LLL CAD in nitrogen was also observed by Moretto-Capelle and coworkers [1] as weak features between 570 eV and 950 eV in the electron spectrum from slow bare N 7+ ions approaching a Si surface. In a similar experiment, Folkerts et al [2] studied electron spectra arising from collisions of C 6+ and N 7+ ions on a Ni surface, also detecting distinct peaks at about twice the ordinary Auger energy (i.e., around 592 eV).…”

“…Multi-electron relaxation processes are of fundamental importance for the understanding of correlation in bound systems. Their study was stimulated for instance in connection with the decay of the so-called hollow atoms, which can be produced in the course of neutralization of slow highly charged ions at surfaces [1,2] or upon irradiation of matter by high-intensity x-ray free-electron lasers (FELs) [3]. The interaction between intense, high-energy light pulses and matter has become a very active field of research and one of today's most exciting topics in atomic and molecular science.…”

Estimation of the ratio of double and single Auger transition rates for the L shell of Kr, Nb and Gd

“…Vaeck and Hansen [6] studied from a theoretical point of view the probability for double Auger decay of multiply excited states in N with two 1s vacancies. On the experimental side, Moretto-Capelle and co-workers [7] observed double Auger lines in collisions of N 7+ ions interacting with a Si surface, while Folkerts and coworkers [8] studied three-electron Auger processes occurring in collisions of C 6+ and N 7+ bare ions on a Ni surface.…”

Three-Electron Auger Process from Beam-Foil Excited Multiply Charged Ions

“…One way to prepare such ''hollow atoms'' (or, in some cases ''hollow ions''), is via target electron capture to outer shells (a ''feeding of excited projectile states'' from the reservoir of target electrons) of slow highly charged ions approaching a surface. This was shown experimentally by Moretto-Capelle et al [3] and Folkerts et al [4]. Another possibility is the formation of inner shell vacancies with non-negligible probability of producing two inner shell vacancies (in the percent range) in ion-atom collisions with nearly symmetric collision systems as first reported by Afrosimov et al [5].…”

“…This may, however, be achieved in future dedicated experiments with the measurement of a complete angular distribution with small angular steps, better time-of-flight resolution, and by carefully ''preparing'' the ion configuration via the target thickness dependence of the ion configuration. The observation of such rare processes [3][4][5][6][7][8][9] is possible only under particular experimental conditions such as highly charged ions plus electron capture at surfaces [4], channeling [10], or, as in the present case, a beam-foil method combined with a powerful detector. This latter method opens the door to detailed studies of the dynamics and complex mechanisms of the electron excitation process inside a solid which are not yet quantitatively understood.…”