Effects of projectile track charging on the H− secondary ion velocity distribution

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2007-03, Vol.256 (1), p.483-488
• Main Authors: Iza, P., Farenzena, L.S., da Silveira, E.F.
• Format: Article
• Language: English
• Subjects: Energy and angle differential spectrometry; H− desorption; Ion solid interaction; Secondary ion emission; SEID; Sputtering; XY-TOF
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/j.nimb.2006.12.070

The bombardment of insulating targets by MeV projectiles produces a positive track delivering secondary electrons to the solid. These electrons are eventually captured by adsorbed hydrogen-containing molecules, inducing fragmentation and initiating the H− secondary ion emission. The dynamics of this process is very sensitive to the track electric field and depends on the emission site and on the H− initial velocity. In this work, a model, based on a time-depending track potential followed by secondary electron induced desorption – SEID, is employed to describe the production and dynamics of H− secondary ion emission. It is shown that depending on how fast the track neutralization occurs, the movement of H− ions may be accelerated, decelerated or even aborted. Trajectories, angular distributions and energy distributions are predicted and compared with experimental data obtained for water ice bombarded by 1.7MeV nitrogen ions.