RESUMEN
Probabilities and cross sections for charge transfer by He2+ impact on atomic hydrogen (H), deuterium (D), and tritium (T) at low collision energies are calculated. The results are obtained using an ab initio theory, which solves the time-dependent Schrödinger equation. For the H target, excellent agreement is achieved between the present and previous results. Differences by orders of magnitude are observed between the cross sections for H, D, and T. A method is introduced to separate the contributions of charge-transfer mechanisms due to radial and rotational coupling. The large differences observed for H, D, and T are attributed to isotope effects in the rotational coupling mechanism.
RESUMEN
The dissipation of potential energy of multiply charged Ar ions incident on Cu has been studied by complementary electron spectroscopy and calorimetry at charge states between 2 and 10 and kinetic energies between 100 eV and 1 keV. The emitted and deposited fractions of potential energy increase at increasing charge state, showing a significant jump for charge states q>8 due to the presence of L-shell vacancies in the ion. Both fractions balance the total potential energy, thus rendering former hypotheses of a significant deficit of potential energy obsolete. The experimental data are reproduced by computer simulations based on the extended dynamic classical-over-the-barrier model.
RESUMEN
We report unprecedented transmission experiments of 3 keV Ne7+ ions through capillaries of 100 nm diameter and 10 microm length produced by etching ion tracks in a polymer foil. We studied foils tilted up to +/-20 degrees for which the incident ions are forced to interact with the capillary surface. Surprisingly, the majority of Ne7+ ions were found to survive the surface scattering events in their initial charge state. The angular distributions of the transmitted particles indicate propagation of the Ne7+ ions along the capillary axis. This capillary guiding of the Ne7+ ion provides evidence that the inner walls of the capillaries become charged and electron capture from the surface is suppressed in a self-organizing process.
RESUMEN
A new form of potential sputtering has been found for impact of slow ( < or = 1500 eV) multiply charged Xe ions (charge states up to q = 25) on MgO(x). In contrast to alkali-halide or SiO2 surfaces this mechanism requires the simultaneous presence of electronic excitation of the target material and of a kinetically formed collision cascade within the target in order to initiate the sputtering process. This kinetically assisted potential sputtering mechanism has been identified to be present for other insulating surfaces as well.