Extremely short-lived reaction resonances in Cl + HD ( v = 1) → DCl + H due to chemical bond softening

Abstract

The Cl + H2 reaction is an important benchmark system in the study of chemical reaction dynamics that has always appeared to proceed via a direct abstraction mechanism, with no clear signature of reaction resonances. Here we report a high-resolution crossed-molecular beam study on the Cl + HD (v = 1, j = 0) → DCl + H reaction (where v is the vibrational quantum number and j is the rotational quantum number). Very few forward scattered products were observed. However, two distinctive peaks at collision energies of 2.4 and 4.3 kilocalories per mole for the DCl (v' = 1) product were detected in the backward scattering direction. Detailed quantum dynamics calculations on a highly accurate potential energy surface suggested that these features originate from two very short-lived dynamical resonances trapped in the peculiar H-DCl (v' = 2) vibrational adiabatic potential wells that result from chemical bond softening. We anticipate that dynamical resonances trapped in such wells exist in many reactions involving vibrationally excited molecules.

Observation of magnetically tunable Feshbach resonances in ultracold 23 Na 40 K + 40 K collisions

“…Recently, significant progress has been achieved in experimentally studying resonances in cold molecular collisions involving the light particles, e.g., H 2 , HD molecule or He atom, by means of molecular beam techniques. In the crossed-beam or merged-beam experiments, shape resonances or Feshbach resonances have been observed in atom-molecule chemical reactions [3][4][5][6][7][8], atom-molecule inelastic collisions [9][10][11], and molecule-molecule inelas- * These authors contributed equally to this work. tic collisions [12,13].…”

Observation of the geometric phase effect in the H + HD → H 2 + D reaction

“…Quantum reactive scattering studies by Kendrick and co-workers and by Althorpe and co-workers established that the GP effect should be negligible at total energy below 1.8 eV (19,(22)(23)(24)(25), becoming significant only at total energy above 3.5 eV. Theoretical studies also pointed out that a clear signature of the GP effect on this reaction would be a shift of the fast angular oscillation in DCSs in the sideways scattering direction (19,26).Over the past two decades, high-resolution crossed beam studies using the H atom tagging method have probed many important elementary reactions (27)(28)(29)(30), including the H + D 2 and H + HD reactions at various collision energies (20,21,(31)(32)(33). No fast angular oscillations in DCSs for these latter reactions have been observed, most likely because the angular resolution…”

“…Over the past two decades, high-resolution crossed beam studies using the H atom tagging method have probed many important elementary reactions (27)(28)(29)(30), including the H + D 2 and H + HD reactions at various collision energies (20,21,(31)(32)(33). No fast angular oscillations in DCSs for these latter reactions have been observed, most likely because the angular resolution of the experimental method was limited.…”

Accurate potential energy surfaces for hydrogen abstraction reactions: A benchmark study on the XYG3 doubly hybrid density functional

“…It is well‐known that dynamics study of reactions with vibrationally excited reactants often requires PESs with higher accuracy. This has been demonstrated before in the F/Cl + H 2 cases . Here, we have tested the H + CHD 3 → H 2 + CD 3 reaction with the CH bond in its ν CH = 0 and 1 states.…”