Charge transfer during pyridine ion scattering off clean and oxygen modified Ni(111)

Wainhaus, Samuel B.; Burroughs, John A.; Hanley, Luke

doi:10.1016/0039-6028(95)00805-5

Cited by 8 publications

(8 citation statements)

References 38 publications

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“…Of course, a strictly linear arrangement is unnecessary for the reactions with CH 3 ϩ ; a slight "off-axis" approach (i.e., when the a, b angle deviates from 180 degrees) can also lead to similar products. The importance of orbital interactions has been recognized, for example, for ion reactions at clean and oxygen-modified Ni (111) surfaces [7].…”

Section: Computational Resultsmentioning

confidence: 99%

“…Reactions in each category can occur via multiple mechanisms, and often it is difficult to distinguish the various pathways [4,5]. The remarkably large number of proposed mechanisms provides evidence of the vast multitude of possibilities [1][2][3][4][5][6][7][8][9].…”

mentioning

confidence: 99%

“…There is a general consensus regarding the overall neutralization process: Neutralization of a positively charged projectile occurs via electron transfer from the surface. Although the electron-transfer mechanism is difficult to describe (for attempts, see, e.g., Reference [7] and references therein), it is supported by several experimental observations, including surface-induced dissociation (SID) efficiency measurements [1,2,[7][8][9] and thermochemical and quantum chemical calculations [9]. It should be noted that ion-surface collisions of atomic projectiles with bare metal surfaces [10] must be distinguished from collisions between small organic (polyatomic) ions and a metal surface covered with an ordered (long chain) self-assembled organic monolayer (SAM).…”

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confidence: 99%

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Neutralization of methyl cation via chemical reactions in low-energy ion-surface collisions with fluorocarbon and hydrocarbon self-assembled monolayer films

Somogyi

Smith

Wysocki

et al. 2002

J. Am. Soc. Mass Spectrom.

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Low-energy ion-surface collisions of methyl cation at hydrocarbon and fluorocarbon self-assembled monolayer (SAM) surfaces produce extensive neutralization of CH3+. These experimental observations are reported together with the results obtained for ion-surface collisions with the molecular ions of benzene, styrene, 3-fluorobenzonitrile, 1,3,5-triazine, and ammonia on the same surfaces. For comparison, low-energy gas-phase collisions of CD3+ and 3-fluorobenzonitrile molecular ions with neutral n-butane reagent gas were conducted in a triple quadrupole (QQQ) instrument. Relevant MP2 6-31G*//MP2 6-31G* ab initio and thermochemical calculations provide further insight in the neutralization mechanisms of methyl cation. The data suggest that neutralization of methyl cation with hydrocarbon and fluorocarbon SAMs occurs by concerted chemical reactions, i.e., that neutralization of the projectile occurs not only by a direct electron transfer from the surface but also by formation of a neutral molecule. The calculations indicate that the following products can be formed by exothermic processes and without appreciable activation energy: CH4 (formal hydride ion addition) and C2H6 (formal methyl anion addition) from a hydrocarbon surface and CH3F (formal fluoride addition) from a fluorocarbon surface. The results also demonstrate that, in some cases, simple thermochemical calculations cannot be used to predict the energy profiles because relatively large activation energies can be associated with exothermic reactions, as was found for the formation of CH3CF3 (formal addition of trifluoromethyl anion).

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Section: Computational Resultsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Neutralization of methyl cation via chemical reactions in low-energy ion-surface collisions with fluorocarbon and hydrocarbon self-assembled monolayer films

Somogyi

Smith

Wysocki

et al. 2002

J. Am. Soc. Mass Spectrom.

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“…Several explanations have been proposed for the observed trends in scattered ion efficiency when SAM films are used as collision targets. The dramatically different efficiency values for hydrocarbon versus fluorinated films suggest that electron transfer from surface chains is one of the main pathways involved in ion neutralization, but other pathways might also contribute . The possibility exists that ion neutralization may occur at localized regions of incomplete monolayer formation that are known to be present, albeit at low concentrations, within monolayer films (e.g., see Figure b).…”

mentioning

confidence: 99%

“…The dramatically different efficiency values for hydrocarbon versus fluorinated films suggest that electron transfer from surface chains is one of the main pathways involved in ion neutralization, but other pathways might also contribute. 21 The possibility exists that ion neutralization may occur at localized regions of incomplete monolayer formation that are known to be present, albeit at low concentrations, within monolayer films (e.g., see Figure 1b). Pinholes or other defect sites that expose the gold substrate might act as sites Langmuir 1997, where ion neutralization could occur with greater probability than at the organic layer.…”

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confidence: 99%

Neutralization of Polyatomic Ions at Self-Assembled Monolayer Surfaces before and after Electrodeposition of Poly(phenylene oxide)

1997

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Self-assembled monolayer (SAM) films chemisorbed onto polycrystalline gold substrates have been shown to be effective targets in ion surface collision investigations. One concern has been whether localized defect sites within SAM films (pinholes) influence the amount of ion neutralization that occurs at the surface. Two molecular ion probes, benzene and DMSO-d 6, are employed to measure the degree of neutralization of a selected monolayer. In this investigation, the behavior of these probes upon collision with SAM surfaces composed of CH3(CH2)3S−Au (C4), CH3(CH2)17S−Au (C18), and CF3(CF2)7(CH2)2S−Au (CF) is compared to the behavior of the same SAM surfaces after potential defect sites have been modified by electrodeposition of poly(phenylene oxide). Plots of total ion current vs time show no change in the scattered ion efficiency as a result of the chemical treatment for any of the monolayer films, even in the case of C4 where the CV electrodeposition experiments indicate exposed gold. The results indicate that neutralization of the ion beam that occurs for each SAM film is not a result of the presence of defect sites within the monolayer films. Furthermore, the results also suggest that the C18 and CF surfaces used routinely in surface-induced dissociation experiments in this laboratory do not contain a significant number of defect sites that expose gold.

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3.9.12 RuO2 - 3.9.18 Tables of selected adsorbate properties

Freund¹,

Kuhlenbeck²

Adsorbed Layers on Surfaces. Part 5: Adsorption of Molecules on Metal, Semiconductor and Oxide Surfaces

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Charge transfer during pyridine ion scattering off clean and oxygen modified Ni(111)

Cited by 8 publications

References 38 publications

Neutralization of methyl cation via chemical reactions in low-energy ion-surface collisions with fluorocarbon and hydrocarbon self-assembled monolayer films

Neutralization of methyl cation via chemical reactions in low-energy ion-surface collisions with fluorocarbon and hydrocarbon self-assembled monolayer films

Neutralization of Polyatomic Ions at Self-Assembled Monolayer Surfaces before and after Electrodeposition of Poly(phenylene oxide)

3.9.12 RuO2 - 3.9.18 Tables of selected adsorbate properties

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