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Manipulating tunnelling gateways in condensed phase isomerization
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  • Arnab Choudhury,
  • Shreya Sinha,
  • David Harlander,
  • Jessalyn DeVine,
  • Alexander Kandratsenka,
  • Peter Saalfrank,
  • Dirk Schwarzer,
  • Alec Wodtke
Arnab Choudhury
Max Planck Institute for Multidisciplinary Sciences - Fassberg Campus
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Shreya Sinha
University of Potsdam
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David Harlander
University of Göttingen
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Jessalyn DeVine
Max Planck Institute for Multidisciplinary Sciences - Fassberg Campus
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Alexander Kandratsenka
Max Planck Institute for Multidisciplinary Sciences - Fassberg Campus
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Peter Saalfrank
University of Potsdam
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Dirk Schwarzer
Max Planck Institute for Multidisciplinary Sciences
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Alec Wodtke
Max Planck Institute for Multidisciplinary Sciences - Fassberg Campus

Corresponding Author:alec.wodtke@mpibpc.mpg.de

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Abstract

When a chemical reaction occurs via tunnelling, a simple mass-dependence is expected, where substitution of atoms by heavier isotopes leads to a reduced reaction rate. However, as shown in a recent study of CO orientational isomerization at the NaCl(100) interface [Choudhury et al., Nature 612, 691 (2022)], the lightest isotopologue need not exhibit the fastest tunnelling; for the CO/NaCl system, the non-monotonic mass-dependence is understood through a new picture of condensed phase tunnelling where the overall rate is dominated by a few pairs of reactant/product states. These state-pairs – termed quantum gateways – gain dynamical importance through accidentally-enhanced tunnelling probabilities, facilitated by a confluence of the energetic landscape underlying the reaction as well as the phonon bath of the surrounding medium. Here, we explore gateway tunnelling through measurements of the kinetic isotope effect (KIE) for CO isomerization in a monolayer buried by many layers of either CO or N2. With an N2 overlayer, tunnelling rates are accelerated for all four isotopologues (12C16O, 13C16O, 12C18O, and 13C18O), but the degree of acceleration is isotopologue-specific and non-intuitively mass dependent. A one-dimensional tunnelling model involving an Eckart barrier cannot capture this behaviour. This reflects how a change to the potential energy surface moves states in and out of resonance, changing which tunnelling gateways can be accessed in the isomerization reaction.
07 Mar 2023Submitted to Natural Sciences
08 Mar 2023Submission Checks Completed
08 Mar 2023Assigned to Editor
13 Mar 2023Reviewer(s) Assigned
12 Apr 2023Review(s) Completed, Editorial Evaluation Pending
12 Apr 2023Editorial Decision: Revise Minor
22 Apr 20231st Revision Received
26 Apr 2023Submission Checks Completed
26 Apr 2023Assigned to Editor
26 Apr 2023Review(s) Completed, Editorial Evaluation Pending
26 Apr 2023Editorial Decision: Accept