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Title: Quantum-state-resolved reactivity of overtone excited CH 4 on Ni(111): Comparing experiment and theory

Quantum state resolved reactivity measurements probe the role of vibrational symmetry on the vibrational activation of the dissociative chemisorption of CH 4 on Ni(111). IR-IR double resonance excitation in a molecular beam was used to prepare CH 4 in three different vibrational symmetry components A 1, E, and F 2 of the 2ν 32 antisymmetric stretch overtone vibration as well as in the ν1+ν3 symmetric plus antisymmetric C-H stretch combination band of F 2 symmetry. We measured the quantum state specific dissociation probability S 0 (sticking coefficient) for each of the four vibrational states by detecting chemisorbed carbon on Ni(111) as the product of CH 4 dissociation by Auger electron spectroscopy. We also observe strong mode specificity, where S 0 for the most reactive state ν 13 is an order of magnitude higher than for the least reactive, more energetic 2ν 3-E state. Our first principles quantum scattering calculations show that as molecules in the ν1 state approach the surface, the vibrational amplitude becomes localized on the reacting C-H bond, making them very reactive. We found that this behavior results from the weakening of the reacting C-H bond as the molecule approaches the surface, decoupling its motion from themore » three non-reacting C-H stretches. Similarly, we find that overtone normal mode states with more ν 1 character are more reactive: S 0(2ν 1) > S 013) > S 0(2ν 3). The 2ν 3 eigenstates excited in the experiment can be written as linear combinations of these normal mode states. The highly reactive 2ν 1 and ν 13 normal modes, being of A 1 and F 2 symmetry, can contribute to the 2ν 3-A 1 and 2ν 3-F 2 eigenstates, respectively, boosting their reactivity over the E component, which contains no ν 1 character due to symmetry.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2] ; ORCiD logo [2]
  1. Swiss Federal Institute of Technology in Lausanne (Switzerland). Lab of Molecular and Chemical Physics
  2. Univ. of Massachusetts, Amherst, MA (United States). Dept. of Chemistry
Publication Date:
Grant/Contract Number:
FG02-87ER13744
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 146; Journal Issue: 5; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
Univ. of Massachusetts, Amherst, MA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS
OSTI Identifier:
1344086

Hundt, P. Morten, van Reijzen, Maarten E., Beck, Rainer D., Guo, Han, and Jackson, Bret. Quantum-state-resolved reactivity of overtone excited CH 4 on Ni(111): Comparing experiment and theory. United States: N. p., Web. doi:10.1063/1.4975025.
Hundt, P. Morten, van Reijzen, Maarten E., Beck, Rainer D., Guo, Han, & Jackson, Bret. Quantum-state-resolved reactivity of overtone excited CH 4 on Ni(111): Comparing experiment and theory. United States. doi:10.1063/1.4975025.
Hundt, P. Morten, van Reijzen, Maarten E., Beck, Rainer D., Guo, Han, and Jackson, Bret. 2017. "Quantum-state-resolved reactivity of overtone excited CH 4 on Ni(111): Comparing experiment and theory". United States. doi:10.1063/1.4975025. https://www.osti.gov/servlets/purl/1344086.
@article{osti_1344086,
title = {Quantum-state-resolved reactivity of overtone excited CH 4 on Ni(111): Comparing experiment and theory},
author = {Hundt, P. Morten and van Reijzen, Maarten E. and Beck, Rainer D. and Guo, Han and Jackson, Bret},
abstractNote = {Quantum state resolved reactivity measurements probe the role of vibrational symmetry on the vibrational activation of the dissociative chemisorption of CH4 on Ni(111). IR-IR double resonance excitation in a molecular beam was used to prepare CH4 in three different vibrational symmetry components A1, E, and F2 of the 2ν32 antisymmetric stretch overtone vibration as well as in the ν1+ν3 symmetric plus antisymmetric C-H stretch combination band of F2 symmetry. We measured the quantum state specific dissociation probability S0 (sticking coefficient) for each of the four vibrational states by detecting chemisorbed carbon on Ni(111) as the product of CH4 dissociation by Auger electron spectroscopy. We also observe strong mode specificity, where S0 for the most reactive state ν1+ν3 is an order of magnitude higher than for the least reactive, more energetic 2ν3-E state. Our first principles quantum scattering calculations show that as molecules in the ν1 state approach the surface, the vibrational amplitude becomes localized on the reacting C-H bond, making them very reactive. We found that this behavior results from the weakening of the reacting C-H bond as the molecule approaches the surface, decoupling its motion from the three non-reacting C-H stretches. Similarly, we find that overtone normal mode states with more ν1 character are more reactive: S0(2ν1) > S0(ν1+ν3) > S0(2ν3). The 2ν3 eigenstates excited in the experiment can be written as linear combinations of these normal mode states. The highly reactive 2ν1 and ν1+ν3 normal modes, being of A1 and F2 symmetry, can contribute to the 2ν3-A1 and 2ν3-F2 eigenstates, respectively, boosting their reactivity over the E component, which contains no ν1 character due to symmetry.},
doi = {10.1063/1.4975025},
journal = {Journal of Chemical Physics},
number = 5,
volume = 146,
place = {United States},
year = {2017},
month = {2}
}

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