Evidence of Simultaneous Double-Electron Promotion in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi mathvariant="normal">F</mml:mi><mml:mo>+</mml:mo></mml:msup></mml:math>Collisions with Surfaces

Mace, Jonathan; Gordon, Michael J.; Giapis, Konstantinos P.

doi:10.1103/physrevlett.97.257603

Cited by 27 publications

(21 citation statements)

References 19 publications

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“…The inelastic collisions include both the electron excitation and direct ionization processes. The molecular orbital (MO) promotion model has been successfully employed in ion surface collisions 33,37,44 to describe the electronic excitation process. We shall not give a detailed description of it here, but briefly point out the general characteristics of excitation processes for positive-ion production.…”

Section: A Positive-ion Productionmentioning

confidence: 99%

“…The H − formation on a Si surface has been studied experimentally and theoretically. [31][32][33][34][35][36][37][38][39] The s character of the H − ion state is particularly simple because there is only one orientation of the atomic state with respect to the surface. In contrast, only a few studies on other types of negative ions have been performed so far.…”

Section: Introductionmentioning

confidence: 99%

“…25 As far as we know, there are only a few studies on semiconductor surfaces. [26][27][28][29][30][31][32][33][34][35][36][37][38][39] Most of these studies mainly involved the neutralization and negative-ion formation of positive projectiles scattering on silicon surfaces. The H − formation on a Si surface has been studied experimentally and theoretically.…”

Section: Introductionmentioning

confidence: 99%

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

Chen

Qiu

Xiong

et al. 2015

The Journal of Chemical Physics

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The dependence of the negative-ion fractions on incident energy and angle is reported for 8.5-22.5 keV F(-) ions scattered from a Si(100) surface at a fixed scattering angle of 38°. The negative-ion fraction increases monotonically with incident velocity for specular scattering. In particular, the variation of the fraction with incident angle is bell shaped for a given incident energy. We interpret this variation using the incident-velocity effect at short distances where the yield of negative ions depends on the number of initial neutrals. It strongly indicates that at short distances, a dynamical equilibrium population is never achieved. This nonadiabatic feature is supported by simple calculations using modified rate equations.

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Section: A Positive-ion Productionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Chen

Qiu

Xiong

et al. 2015

The Journal of Chemical Physics

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“…Experiments were conducted in a scattering apparatus [15,19] with mass-selected and energy-tuned hyperthermal N þ and O þ ion beams interacting with O atoms adsorbed onto Pt and Pd surfaces. The ion beams were extracted from a plasma discharge, operating at 5 mTorr with a feed of N 2 =Ar=Ne and O 2 =Ar=Ne mixtures, respectively.…”

Section: Direct or Eley-rideal Reactions Between Energetic Nmentioning

confidence: 99%

Kinematics of Eley-Rideal Reactions at Hyperthermal Energies

Yao

Giapis

2016

Phys. Rev. Lett.

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Direct or Eley-Rideal reactions between energetic N þ and O þ projectiles and O atoms, adsorbed onto Pt and Pd surfaces, are studied experimentally at incidence energies between 20 and 200 eV. The exit energies of the diatomic molecular products NO and O 2 depend linearly on the incidence energy of the corresponding projectiles. A reaction mechanism is proposed, where the incident projectile collides with a single metal atom on the surface, linked to an adsorbed O atom. At the apsis point, a high-energy transient state is formed between the projectile, substrate, and adsorbate atoms. As the projectile begins to rebound, the transient state decomposes into a diatomic molecule, consisting of the original projectile and the adsorbed O atom, which exits the surface with memory of the incidence energy. Energy and momentum conservation during this single-bounce event (atom in, molecule out) accurately predict the exit energy of the molecular product, thus capturing the kinematics of the direct reaction. DOI: 10.1103/PhysRevLett.116.253202 Gas-surface reactions are often thought to proceed between two extremes: the Langmuir-Hinshelwood (LH) mechanism, which requires all reactants to be adsorbed onto and in thermal equilibrium with the surface, and the Eley-Rideal (ER) mechanism, where an energetic reactant (the "projectile") impinges onto a surface adsorbate and bonds with it directly [1]. The LH mechanism applies to most surface chemical reactions and is well understood [2]. The ER mechanism is still being debated: the rarity of chemical environments where hyperthermal reactive species bombard surfaces, combined with experimental difficulties in detecting energetic reaction products, has impeded progress in understanding such reactions. In fact, even the definition of an ER reaction is outright crude: the notion of a bond forming between an energetic projectile and a surface adsorbate in a head-on collision, followed up by ejection from the surface of an energetic reaction product, violates momentum conservation. This problem does not arise if the projectile collides first with the surface. Hot atom reactions represent an intermediate mechanism, where the projectile undergoes few bounces before reacting with an adsorbate [3]. Owing to multiple collisions, which lead to variable energy losses, these do not qualify as prompt ER reactions.What comprises an ER reaction? The literature consensus suggests that ER reactions should have at least the following attributes: (i) they require a gas-phase projectile with high kinetic or potential energy, impinging onto an adsorbate-covered surface; (ii) they yield a fast-moving molecular product, consisting of the projectile-adsorbate combination, which leaves the surface (no trapping); and (iii) the product translational energy must be directly correlated to the energy of the incident projectile. Secondary attributes include that (iv) the product molecule may be internally excited; and (v) the product angular flux distribution deviates from the cosine law, with subspecular pref...

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“…This method, however, is confronted by difficulties similar to those involved in probing individual T-T collisions. The problems can be easily resolved by using low energy ion spectroscopy (LEIS) and direct recoil spectroscopy (DRS), which were both used previously to study ionization by promotion in P-T collisions [11][12][13][14][15][16][17]. Similar to scattered projectiles, direct recoils are atomic particles emitted at relatively high energies compared to sputtered particles [18].…”

Section: Introductionmentioning

confidence: 99%