Inelastic and reactive scattering dynamics of hyperthermal oxygen atoms on ionic liquid surfaces

[emim][NTf2] and [C12mim][NTf 2]

Bohan Wu, Jianming Zhang, Timothy K. Minton, Kenneth G. McKendrick, John M. Slattery, Scott Yockel, George C Schatz

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Abstract

Collisions of hyperthermal oxygen atoms, with an average translational energy of 520 kJ mol-1, on continuously refreshed ionic liquids, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([emim][NTf 2]) and 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C12mim][NTf2]), were studied with the use of a beam-surface scattering technique. Time-of-flight and angular distributions of inelastically scattered O and reactively scattered OH and H2O were collected for various angles of incidence with the use of a rotatable mass spectrometer detector. For both O and OH, two distinct scattering processes were identified, which can be empirically categorized as thermal and non-thermal. Non-thermal scattering is more probable for both O and OH products. The observation of OH confirms that at least some reactive sites, presumably alkyl groups, must be exposed at the surface. The ionic liquid with the longer alkyl chain, [C12mim][NTf2], is substantially more reactive than the liquid with the shorter alkyl chain, [emim][NTf2], and proportionately much more so than would be predicted simply from stoichiometry based on the number of abstractable hydrogen atoms. Molecular dynamics models of these surfaces shed light on this change in reactivity. The scattering behavior of O is distinctly different from that of OH. However, no such differences between inelastic and reactive scattering dynamics have been seen in previous work on pure hydrocarbon liquids, in particular the benchmark, partially branched hydrocarbon, squalane (C30H62). The comparison between inelastic and reactive scattering dynamics indicates that inelastic scattering from the ionic liquid surfaces takes place predominantly at non-reactive sites that are effectively stiffer than the reactive alkyl chains, with a higher proportion of collisions sampling such sites for [emim][NTf 2] than for [C12mim][NTf2].

Original languageEnglish
Title of host publicationAIP Conference Proceedings
Pages516-521
Number of pages6
Volume1333
EditionPART 1
DOIs
Publication statusPublished - 2011
Event27th International Symposium on Rarefied Gas Dynamics, RGD27 - Pacific Grove, CA, United States
Duration: Jul 10 2011Jul 15 2011

Other

Other27th International Symposium on Rarefied Gas Dynamics, RGD27
CountryUnited States
CityPacific Grove, CA
Period7/10/117/15/11

Fingerprint

liquid surfaces
oxygen atoms
inelastic scattering
scattering
imides
liquids
hydrocarbons
collisions
dynamic models
mass spectrometers
stoichiometry
hydrogen atoms
proportion
angular distribution
reactivity
incidence
sampling
molecular dynamics
detectors
products

Keywords

  • Hyperthemal atomic oxygen
  • Ionic liquid
  • Scattering dynamics

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Wu, B., Zhang, J., Minton, T. K., McKendrick, K. G., Slattery, J. M., Yockel, S., & Schatz, G. C. (2011). Inelastic and reactive scattering dynamics of hyperthermal oxygen atoms on ionic liquid surfaces: [emim][NTf2] and [C12mim][NTf 2]. In AIP Conference Proceedings (PART 1 ed., Vol. 1333, pp. 516-521) https://doi.org/10.1063/1.3562700

Inelastic and reactive scattering dynamics of hyperthermal oxygen atoms on ionic liquid surfaces : [emim][NTf2] and [C12mim][NTf 2]. / Wu, Bohan; Zhang, Jianming; Minton, Timothy K.; McKendrick, Kenneth G.; Slattery, John M.; Yockel, Scott; Schatz, George C.

AIP Conference Proceedings. Vol. 1333 PART 1. ed. 2011. p. 516-521.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Wu, B, Zhang, J, Minton, TK, McKendrick, KG, Slattery, JM, Yockel, S & Schatz, GC 2011, Inelastic and reactive scattering dynamics of hyperthermal oxygen atoms on ionic liquid surfaces: [emim][NTf2] and [C12mim][NTf 2]. in AIP Conference Proceedings. PART 1 edn, vol. 1333, pp. 516-521, 27th International Symposium on Rarefied Gas Dynamics, RGD27, Pacific Grove, CA, United States, 7/10/11. https://doi.org/10.1063/1.3562700
Wu B, Zhang J, Minton TK, McKendrick KG, Slattery JM, Yockel S et al. Inelastic and reactive scattering dynamics of hyperthermal oxygen atoms on ionic liquid surfaces: [emim][NTf2] and [C12mim][NTf 2]. In AIP Conference Proceedings. PART 1 ed. Vol. 1333. 2011. p. 516-521 https://doi.org/10.1063/1.3562700
Wu, Bohan ; Zhang, Jianming ; Minton, Timothy K. ; McKendrick, Kenneth G. ; Slattery, John M. ; Yockel, Scott ; Schatz, George C. / Inelastic and reactive scattering dynamics of hyperthermal oxygen atoms on ionic liquid surfaces : [emim][NTf2] and [C12mim][NTf 2]. AIP Conference Proceedings. Vol. 1333 PART 1. ed. 2011. pp. 516-521
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abstract = "Collisions of hyperthermal oxygen atoms, with an average translational energy of 520 kJ mol-1, on continuously refreshed ionic liquids, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([emim][NTf 2]) and 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C12mim][NTf2]), were studied with the use of a beam-surface scattering technique. Time-of-flight and angular distributions of inelastically scattered O and reactively scattered OH and H2O were collected for various angles of incidence with the use of a rotatable mass spectrometer detector. For both O and OH, two distinct scattering processes were identified, which can be empirically categorized as thermal and non-thermal. Non-thermal scattering is more probable for both O and OH products. The observation of OH confirms that at least some reactive sites, presumably alkyl groups, must be exposed at the surface. The ionic liquid with the longer alkyl chain, [C12mim][NTf2], is substantially more reactive than the liquid with the shorter alkyl chain, [emim][NTf2], and proportionately much more so than would be predicted simply from stoichiometry based on the number of abstractable hydrogen atoms. Molecular dynamics models of these surfaces shed light on this change in reactivity. The scattering behavior of O is distinctly different from that of OH. However, no such differences between inelastic and reactive scattering dynamics have been seen in previous work on pure hydrocarbon liquids, in particular the benchmark, partially branched hydrocarbon, squalane (C30H62). The comparison between inelastic and reactive scattering dynamics indicates that inelastic scattering from the ionic liquid surfaces takes place predominantly at non-reactive sites that are effectively stiffer than the reactive alkyl chains, with a higher proportion of collisions sampling such sites for [emim][NTf 2] than for [C12mim][NTf2].",
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