H−formation in collisions of hydrogen atoms with Al(100) surfaces

Abstract

We theoretically investigate the electron transfer dynamics during the reflection of hydrogen atoms on an Al(100) surface for a wide range of collision energies below 6 keV. We find a nonmonotonic variation of the hydrogen-negative-ion fractions as functions of the projectile impact velocity due to nonadiabatic electron transfer. Our calculated anion fractions for projectiles scattered along high Miller-index crystal-surface directions are in good quantitative agreement with measured H − fractions for a wide range of exit velocities.

Negative Ions in Space

“…Finally, negatively charged ions can also be formed in collisions of atoms , and positively charged ions with surfaces. There is an ongoing challenge in the investigation of negative-ion formation processes at surfaces relevant to astrophysical environments.…”

“…196 Laboratory experiments indicate that the origin of the anion might be due to photon or cosmic-ray interaction 197 with the ice, although it has also been argued that the anion can be produced by low-temperature thermal reactions between HNCO and NH 3 in ice. 198 Finally, negatively charged ions can also be formed in collisions of atoms 199,200 and positively charged ions 201 with surfaces. There is an ongoing challenge in the investigation of negative-ion formation processes at surfaces relevant to astrophysical environments.…”

Adiabatic Energy Loss in Hyperthermal H Atom Collisions with Cu and Au: A Basis for Testing the Importance of Nonadiabatic Energy Loss

“…At the same time, the energy is low enough that inelastic scattering of H atoms by T→ph and T→ehp are essentially the only open channels for energy loss; the probability of H − formation is less than 0.06%. 48 The first case concerns H incident on Cu(111) with polar angle, θ i = 15°relative to the surface normal and azimuthal angle, ϕ i = 30°relative to the [101] direction. We denote this case as H−Cu(θ i = 15°,ϕ i = 30°).…”

“…Use of high incidence energy is likely to increase the energy loss from nonadiabatic effects. At the same time, the energy is low enough that inelastic scattering of H atoms by T → ph and T → ehp are essentially the only open channels for energy loss; the probability of H – formation is less than 0.06% …”

Nonadiabatic dynamics in energetic negative fluorine ions scattering from a Si(100) surface

“…[13][14][15][16][17][18][19][20][21] Numerous studies of keV-energy atoms and ions scattering on metal surfaces reveal that resonance charge transfer between projectile and surface via electron tunneling is the dominant process. [16][17][18][19][22][23][24] Ion surface scattering is the most direct way to probe the charge exchange process. 25 As far as we know, there are only a few studies on semiconductor surfaces.…”