Research ArticleCHEMICAL PHYSICS

Approaching the forbidden fruit of reaction dynamics: Aiming reagent at selected impact parameters

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Science Advances  05 Oct 2018:
Vol. 4, no. 10, eaau2821
DOI: 10.1126/sciadv.aau2821
  • Fig. 1 Generation of CF2 projectile from the electron-induced dissociation of CF3.

    (A) STM images showing the initial and final states of CF3 dissociation. The tip was placed above the CF3 (white cross) to induce dissociation. The white arrow indicates the recoil direction of the CF2. (B) Distance distribution of CF2 (red squares) and F atom (green squares) along the [Embedded Image] direction (x axis) and the [001] direction (y axis; 1 unit cell = 3.61 Å). (C) CF2 rotation in CF2 ratcheting. (D) CF2 translation in CF2 ratcheting. (E) Alternating kinetic energy of F and C atoms in the ratcheting CF2, obtained from the trajectory in fig. S1 and movie S1.

  • Fig. 2 Effects of different impact parameters, b, on CF2 + CF2 collision.

    (A) STM images and schematics showing the initial and final states of b = 0 collision. (B) Same data for b = 3.61 Å collision. In both panels, the tip was placed above the CF3 (white cross) to produce the CF2 projectile. The black cross marks the initial position of the CF2 target. In the final state for b = 3.61 Å, the dashed circles indicate the new positions of the CF2 projectile and CF2 target (white and black circles, respectively) after the collision.

  • Fig. 3 Effects of different initial projectile-target separation on zero–impact parameter CF2 + CF2 collision.

    The dashed line at ~11 Å demarcates the regime with 100% reaction probability (high CF2 + CF2 collision energy) from that with mixed outcomes (low collision energy). The stacked histogram plot uses a bin size of 2.55 Å (1 unit cell along the [Embedded Image] direction). Assocn means association.

  • Fig. 4 Computed dynamics for “direct” and “indirect” association reactions.

    (A) Trajectory for direct single-collision reaction giving the forward-scattered C2F4 product at 1.5-eV collision energy. (B) Trajectory for indirect double-collision reaction giving the backward-scattered C2F4 product at 1.2-eV collision energy. In both panels, the vertical dashed lines indicate the initial position of the CF2 target. Here, a collision is said to occur when both CF2 have reached their closest-approach distance of 2.55 Å, 1 unit cell along the [Embedded Image] direction (whether the first or the second collision).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/10/eaau2821/DC1

    Supplementary Text

    Fig. S1. Computed dynamics for the electron-induced reaction of CF3, obtained from the I2S model.

    Fig. S2. Distance dependence of the energy in the recoiling CF2.

    Fig. S3. Identification of molecular species on the surface.

    Fig. S4. CF2 + I collision at 1.80 Å impact parameter, giving only momentum transfer from the projectile to the target.

    Fig. S5. Nonreactive outcome of a zero–impact parameter CF2 + CF2 collision, resulting in only momentum transfer from the projectile to the target.

    Fig. S6. Trajectory for direct association reaction superimposed on a restricted cut through the ground potential energy surface.

    Fig. S7. Trajectory for indirect association reaction superimposed on a restricted cut through the ground potential energy surface.

    Fig. S8. Evidence for electron-induced reaction.

    Movie S1. Computed dynamics for the electron-induced reaction of CF3, obtained from the I2S model.

    Movie S2. Computed dynamics for direct reaction.

    Movie S3. Computed dynamics for indirect reaction.

  • Supplementary Materials

    The PDF file includes:

    • Supplementary Text
    • Fig. S1. Computed dynamics for the electron-induced reaction of CF3, obtained from the I2S model.
    • Fig. S2. Distance dependence of the energy in the recoiling CF2.
    • Fig. S3. Identification of molecular species on the surface.
    • Fig. S4. CF2 + I collision at 1.80 Å impact parameter, giving only momentum transfer from the projectile to the target.
    • Fig. S5. Nonreactive outcome of a zero–impact parameter CF2 + CF2 collision, resulting in only momentum transfer from the projectile to the target.
    • Fig. S6. Trajectory for direct association reaction superimposed on a restricted cut through the ground potential energy surface.
    • Fig. S7. Trajectory for indirect association reaction superimposed on a restricted cut through the ground potential energy surface.
    • Fig. S8. Evidence for electron-induced reaction.
    • Legends for movies S1 to S3

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Computed dynamics for the electron-induced reaction of CF3, obtained from the I2S model.
    • Movie S2 (.mp4 format). Computed dynamics for direct reaction.
    • Movie S3 (.mp4 format). Computed dynamics for indirect reaction.

    Files in this Data Supplement:

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