Simulación del tránsito de iones Hn+ a través de láminas delgadas

Abstract

In this Ph.D. Thesis we have created a simulation program that allows us to analyze with great detail experiments of interaction of molecular projectiles with thin foils.

Using the dielectric formalism, we have seen that the electronic stopping of the hydrogen atom is smaller than the electronic stopping of a proton, and that the electronic stopping of the H 2 + and H 3 + molecular ions is also smaller than twice and the three times that of a proton, respectively.

Also, we have studied electronic vicinage effects in the H 2 + -H + system, which are similar to those of the H + -H + system. These vicinage effects tend to align the dissociated fragments from the molecular ions in the beam direction.

We have established a model to incorporate the electronic loss and capture processes by atomic fragments dissociated from hydrogen clusters. We have checked that the electronic loss and capture processes by an atomic projectile are influenced by the presence of neighbor fragments coming from the same dissociation and depend on the distance between them and on the beam velocity.

Concerning the transport of H 2 + molecular ions, we have implemented in the simulation program the recombination process of these ions. It depends on the fact that two protons capture an electron at the exit surface of the foil, besides the system formed by the two protons and the captured electron must have an internal energy smaller than the relative maximum of the effective potential corresponding to the ground electronic level of the H 2 + ion. Also the interproton distance must be comprised between the values of the classic turning points of the effective potential well.

Regarding the transport of H 3 + molecular ions, we have corroborated that the initial geometry of the H 3 + ion is an equilateral triangle, which is the only geometry resulting in two peaks in the energy and the angle spectra. The initial equilateral triangle side distance depends on the experimental conditions and affects in a sizable manner the final results.