Surface Temperature Dependence of Methane Activation on Ni(111)

Killelea, Daniel R.; Campbell, Victoria L.; Shuman, Nicholas S.; Smith, Richard R.; Utz, A. L.

doi:10.1021/jp9065339

Cited by 57 publications

(48 citation statements)

References 46 publications

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“…For the laser-off measurements, the sticking coefficient for T S = 500 K is lower for E trans less than 90 kJ/mol, whereas increasing T S at higher energies does not change S laser-off 0 significantly. This is consistent with previous experiments performed by Utz et al for the dissociative chemisorption of CH 4 on Ni(111), 22,25 where it was found that S ν 3 0 increased more as T S was increased when the total energy (E trans + E vib ) was lower than the barrier height, and S ν 3 0 changed less when the total energy was greater than the barrier height.…”

Section: Resultssupporting

confidence: 93%

“…[15][16][17][18][19][20][21][22] Several techniques have been developed to measure sticking coefficients with quantum state resolution, for example, by detecting the surface bound products using Auger electron spectroscopy, 5,6,23,24 reflection absorption infrared spectroscopy, 7,11,15,21 or titration of the adsorbates to make molecules that desorb and can be detected in the gas phase mass spectrometrically. 9,12,22,25 Whilst these have proved to be powerful techniques for determining quantum state resolved sticking coefficients, they share a common disadvantage in that calibrations are necessary to quantify the adsorbate coverage and number of molecules incident on the surface, both of which need to be known to accurately determine the sticking coefficient.…”

Section: Introductionmentioning

confidence: 99%

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Quantum state resolved molecular beam reflectivity measurements: CH4 dissociation on Pt(111)

Chadwick

Gutiérrez-González

Beck

2016

The Journal of Chemical Physics

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The King and Wells molecular beam reflectivity method has been used for a quantum state resolved study of the dissociative chemisorption of CH4 on Pt(111) at several surface temperatures. Initial sticking coefficients S0 were measured for incident CH4 prepared both with a single quantum of ν3 antisymmetric stretch vibration by infrared laser pumping and without laser excitation. Vibrational excitation of the ν3 mode is observed to be less efficient than incident translational energy in promoting the dissociation reaction with a vibrational efficacy ην3 = 0.65. The initial state resolved sticking coefficient S0ν3 was found to be independent of the surface temperature over the 50 kJ/mol to 120 kJ/mol translational energy range studied here. However, the surface temperature dependence of the King and Wells data reveals the migration of adsorbed carbon formed by CH4 dissociation on the Pt(111) surface leading to the growth of carbon particles.

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Section: Resultssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Quantum state resolved molecular beam reflectivity measurements: CH4 dissociation on Pt(111)

Chadwick

Gutiérrez-González

Beck

2016

The Journal of Chemical Physics

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“…36,37,40,74,75 Another simulation suggests any enhancement of the reaction rate via phonons diminishes with increasing translational or vibrational energy of the incident methane. 76 Recent experimental results support this theory 77 and we plan to explore the role of phonon excitation on methane activation more fully in a future publication. Inelastic tunnelling 11,44,78 or infrared excitation studies of surface-adsorbed species 79 differ in some ways from the beamsurface studies highlighted above, but key features of this framework still apply.…”

Section: Impact Of Ivr On Surface Reactivity and Dynamicsmentioning

confidence: 75%

On the origin of mode- and bond-selectivity in vibrationally mediated reactions on surfaces

Killelea

Utz

2013

Phys. Chem. Chem. Phys.

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On the origin of mode-and bond-selectivity in vibrationally mediated reactions on surfaces. Physical Chemistry Chemical Physics, 15, 47: 20545-20554, 2013 The experimental observations of vibrational mode-and bond-selective chemistry at the gas-surface interface indicate that energy redistribution within the reaction complex is not statistical on the timescale of reaction. Such behavior is a key prerequisite for efforts to use selective vibrational excitation to control chemistry at the technologically important gas-surface interface. This paper outlines a framework for understanding the origin of non-statistical reactivity on surfaces. The model focuses on the kinetic competition between intramolecular vibrational energy redistribution (IVR) within the reaction complex, which in the long-time limit leads to statistical behavior, and quenching, scattering, or desorption processes that restrict the extent of IVR prior to reaction. Characteristic timescales for these processes drawn from studies of vibrational energy flow dynamics on surfaces and in the gas and condensed phases suggest that IVR is severely limited for important classes of surface reactions. Under these conditions, selective vibrational excitation can lead to preferential transition state access and result in mode-or bond-selective chemistry, even at high collision energies above the barrier to reaction. In addition to providing a basis for understanding experimental observations, the model provides guidance for identifying other gas-surface reactions that may exhibit mode-selective behavior.

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“…[1][2][3] The outline of the review is as follows. The first section introduces key concepts and definitions that are used when discussing gas-surface reaction dynamics.…”

Section: Introductionmentioning

confidence: 99%

Quantum state resolved gas–surface reaction dynamics experiments: a tutorial review

Chadwick

Beck

2016

Chem. Soc. Rev.

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We present a tutorial review of our quantum state resolved experiments designed to study gas-surface reaction dynamics. The combination of a molecular beam, state specific reactant preparation by infrared laser pumping, and ultrahigh vacuum surface analysis techniques make it possible to study chemical reactivity at the gas-surface interface in unprecedented detail. We describe the experimental techniques used for state specific reactant preparation and for detection of surface bound reaction products developed in our laboratory. Using the example of the reaction of methane on Ni and Pt surfaces, we show how state resolved experiments uncovered clear evidence for vibrational mode specificity and bond selectivity, as well as steric effects in chemisorption reactions. The state resolved experimental data provides valuable benchmarks for comparison with theoretical models for gas-surface reactivity aiding in the development of a detailed microscopic understanding of chemical reactivity at the gas-surface interface. Key learning points(1) How to prepare beams of quantum state selected molecules through rapid adiabatic passage. (2) Physisorption vs. chemisorption. (3) What is state and mode specificity? (4) What is vibrational bond selectivity? (5) Orientation vs. alignment and alignment dependent reactivity.

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Surface Temperature Dependence of Methane Activation on Ni(111)

Cited by 57 publications

References 46 publications

Quantum state resolved molecular beam reflectivity measurements: CH4 dissociation on Pt(111)

Quantum state resolved molecular beam reflectivity measurements: CH4 dissociation on Pt(111)

On the origin of mode- and bond-selectivity in vibrationally mediated reactions on surfaces

Quantum state resolved gas–surface reaction dynamics experiments: a tutorial review

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