Chemical dynamics of vibrationally excited molecules: Controlling reactions in gases and on surfaces

Crim, F. Fleming

doi:10.1073/pnas.0803010105

Cited by 180 publications

(143 citation statements)

References 69 publications

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“…Crim reviewed detailed studies of C-H bond activation in bimolecular reactions where Cl abstracts an H or D atom from one of methane's vibrationally excited isotopologues. 1 In all cases, C-H or C-D stretching excitation leads to preferential cleavage of the vibrationally excited bond, but mode selective reactivity patterns are more subtle. In CH 3 D, the symmetric C-H stretching vibration is significantly more reactive than the slightly higher energy antisymmetric C-H stretching state.…”

Section: Resultsmentioning

confidence: 99%

“…1 During the past decade, state-resolved gas-surface reactivity and adsorbate excitation studies [2][3][4] have extended the realm of vibrational mode-and bond-selective chemistry from the gas phase to the technologically important gas-surface interface. There are now examples of vibrational mode selective surface chemistry, [5][6][7][8][9][10][11][12] in which the identity of the reagent's vibrational state, and not just its energy, determines reaction probability, and bond selective surface chemistry 13,14 where selective vibrational excitation leads to preferential cleavage of a particular chemical bond.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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“…It is well-known that the vibrational quantum state on a reactant surface can severely influence the ensuing excited state dynamics. [30][31][32][33][34] Indeed, we find in our ultrafast experiments that the CSSs are formed on two distinct timescales representing ET from a hot 3 MLCT ( 3 MLCT*) ( hot = 3.6 ps) and a relaxed 3 MLCT ( cool = 14.7 ps). Note however that we do not find any evidence of (C C) v>0 population in the TRIR data beyond the instrument-limited time resolution of ca.…”

Section: Excited State Dynamics Without Ir Excitationmentioning

confidence: 99%

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

et al. 2017

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Ultrafast electron transfer in condensed-phase molecular systems is often strongly coupled to intramolecular vibrations that can promote, suppress and direct electronic processes. Recent experiments exploring this phenomenon proved that light-induced electron transfer can be strongly modulated by vibrational excitation, suggesting a new avenue for active control over molecular function. Here, we achieve the first example of such explicit vibrational control through judicious design of a Pt(II)-acetylide charge-transfer Donor-Bridge-Acceptor-Bridge-Donor "fork" system: asymmetric 13 C isotopic labelling of one of the two -C≡C-bridges makes the two parallel and otherwise identical Donor→Acceptor electron-transfer pathways structurally distinct, enabling independent vibrational perturbation of either. Applying an ultrafast UV pump (excitation)-IR pump (perturbation)-IR probe (monitoring) pulse sequence, we show that the pathway that is vibrationally perturbed during UV-induced electron-transfer is dramatically slowed down compared to its unperturbed counterpart. One can thus choose the dominant electron transfer pathway. The findings deliver a new opportunity for precise perturbative control of electronic energy propagation in molecular devices. Main TextControlling the function of future advanced materials demands a profound understanding of energymatter interactions in molecular systems at the quantum level. 1 There is a growing consensus that energy-and electron-transfer processes occurring far away from equilibrium in condensed-phase systems on femto-to-picosecond timescales do not conform to the Born-Oppenheimer approximation. Indeed, nuclear and electronic wave functions often strongly interact with each other, leading to exotic phenomena whereby vibrational motion can mediate and dictate the rate and efficiency of electronic transitions. [2][3][4][5] With overwhelming evidence that nuclear-electronic (vibronic) interactions play a crucial role in a broad range of systems, including light harvesting and conversion in photosynthetic organisms, 6-11 this phenomenon represents a tremendous opportunity to acquire deeper knowledge and control over the structural traits that govern molecular function and reactivity.Recent efforts led by Rubtsov et al.,12,13 Bakulin et al., 14 and our group 15,16 have shown that one way to experimentally exploit vibronic coupling to modulate molecular function is to introduce targeted vibrational excitation along specific reaction co-ordinates using ultrafast mid-infrared (IR) pulses. This approach enables promoting or suppressing electronic transitions, notably photo-induced electron transfer (ET), an elementary process that pervades the natural world. Although the demonstrated excited state modulations have been remarkably efficient, up to 100% suppression in one case, 15 predictive and directive control of electron transfer in the condensed phase has not been achieved yet.

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“…Jiang et al justified the observed enhancement in the CHD 3 + Ni(111) reactivity after pre-excitation of the ν 1 mode by considering the large projection that this mode has on the reaction coordinate at the transition state. 15 This argument, which is not specific to gas−surface reactions 49 and considered valid under the assumption that vibrational energy remains localized on the CH stretch, is expected to be valid for our system as well. Note that the theory underestimates the experimental vibrational efficacy because the energy shift between the laser-off and the ν 1 -excited reaction probability curves is lower for the AIMD results than that for the experiments.…”

mentioning

confidence: 99%

Ab Initio Molecular Dynamics Calculations versus Quantum-State-Resolved Experiments on CHD₃ + Pt(111): New Insights into a Prototypical Gas–Surface Reaction

Nattino

Ueta

Chadwick

et al. 2014

J. Phys. Chem. Lett.

127

198

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ABSTRACT:The dissociative chemisorption of methane on metal surfaces is of fundamental and practical interest, being a rate-limiting step in the steam reforming process. The reaction is best modeled with quantum dynamics calculations, but these are currently not guaranteed to produce accurate results because they rely on potential energy surfaces based on untested density functionals and on untested dynamical approximations. To help overcome these limitations, here we present for the first time statistically accurate reaction probabilities obtained with ab initio molecular dynamics (AIMD) for a polyatomic gas-phase molecule reacting with a metal surface. Using a general purpose density functional, the AIMD reaction probabilities are in semiquantitative agreement with new quantum-state-resolved experiments on CHD 3 + Pt(111). The comparison suggests the use of the sudden approximation for treating the rotations even though CHD 3 has large rotational constants and yields an estimated reaction barrier of 0.9 eV for CH 4 + Pt(111). SECTION: Surfaces, Interfaces, Porous Materials, and Catalysis T he steam reforming process, in which methane and water react over a Ni catalyst, is the main commercial source of molecular hydrogen. The dissociation (or dissociative chemisorption) of CH 4 on the catalyst into CH 3 (ad) + H(ad) is a rate-determining step of the full process. 1 Moreover, dissociation of methane on metal surfaces is of fundamental interest. 2−13 Already from early molecular beam experiments, it is known that vibration is very effective in promoting reactivity. 3,4,14 More recently, it has been shown that the reaction is mode-specific, that is, the degree to which energizing the molecule promotes reaction depends on whether the energy is put in translation or vibration and even on which vibration it is put in (vibrational mode specificity). 5−8 These observations, which have been explained qualitatively on the basis of different models, 9,15 rule out the application of fully statistical models. For some vibrational modes, the vibrational efficacy, which measures how effective putting energy into vibration is at promoting reaction relative to increasing the incidence energy (E i ), is even larger than one. 7,10 In addition, the dissociation of partially deuterated molecules shows bond selectivity; for instance, in CHD 3 , the CH bond can be selectively broken upon excitation to an appropriate initial vibrational state. 11,12 Finally, dissociative chemisorption of methane on metal surfaces represents a current frontier in the theoretical description of the dynamics of reactions of gas-phase molecules on metal surfaces, 15−24 with much current efforts now being aimed at achieving an accurate description of this reaction through high-dimensional quantum dynamics calculations. 16,23,24 A wealth of experiments exist for the methane + Pt(111) system. 3,8,12,17,25−29 There has been considerable debate 2,25 concerning the importance of tunneling in this and similar systems. Recent calculations 17,23,30 suggest only a...

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Chemical dynamics of vibrationally excited molecules: Controlling reactions in gases and on surfaces

Cited by 180 publications

References 69 publications

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

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

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

Ab Initio Molecular Dynamics Calculations versus Quantum-State-Resolved Experiments on CHD₃ + Pt(111): New Insights into a Prototypical Gas–Surface Reaction

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Chemical dynamics of vibrationally excited molecules: Controlling reactions in gases and on surfaces

Cited by 180 publications

References 69 publications

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

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

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

Ab Initio Molecular Dynamics Calculations versus Quantum-State-Resolved Experiments on CHD3 + Pt(111): New Insights into a Prototypical Gas–Surface Reaction

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Ab Initio Molecular Dynamics Calculations versus Quantum-State-Resolved Experiments on CHD₃ + Pt(111): New Insights into a Prototypical Gas–Surface Reaction