Research ArticleMOLECULAR PHYSICS

Quantum unidirectional rotation directly imaged with molecules

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Science Advances  03 Jul 2015:
Vol. 1, no. 6, e1400185
DOI: 10.1126/sciadv.1400185
  • Fig. 1 Schematic of experimental setup and the space-fixed axis system used.

    The upper-left image shows the definition of the present space-fixed axis system, in which the laser propagates toward the z direction and the polarization of the first pulse is parallel to the y axis. All the electric field vectors of the three pulses are in the xy plane. The polar angle is θ, and the azimuthal angle is φ. Because the laser polarizations define the plane of rotation, in this case, time dependence with respect to φ in the xy plane characterizes unidirectional rotation dynamics. The apparatus consists of ion optics (a set of gridless lens electrodes), a mechanical slit, a pulsed repeller, and a 2D position sensitive detector (MCP/screen/camera). The detector surface is parallel to the xy plane so that the angle φ of the ejected direction for the Coulomb exploded fragments can be directly measured from the 2D image. The four insets show typical observed images of the fragment ions (after the calibration to make the images circles).

  • Fig. 2 Selected snapshots of rotational wave packet dynamics induced by a single linearly polarized pulse.

    (Bottom) Observed N3+ ion images (after the calibration). The double ring structure comes from the two channels of Coulomb explosion (N3+ from N24+ and N25+), in which higher-charge states lead to larger kinetic energy release (outer ring). (Top) Polar plots of the observed angular probability. The polarization of the pulse is vertical in this figure.

  • Fig. 3 Time-dependent angular distributions and selected snapshots of unidirectional molecular rotation.

    (A) Observed time- and angular-dependent probability, P(θ = π/2,φ,t), in the rotational wave packet dynamics. Before t = 0, molecules are randomly oriented and therefore the probability is just 1/4π ~ 0.08. (B) Simulated plot corresponding to (A), with the laser intensity set to 15 TW/cm2. (C) Polar plots of the observation in (A), in which the probability is displayed as a radius from the origin. The plots show the dynamics in the xy plane, and the first pulse polarization is vertical, whereas the second is tilted 45° to the left. Selected snapshots during the revival time, Trev, after the second pulse irradiation are shown.

  • Fig. 4 Comparison of experimental and theoretical wave packet dynamics.

    (Top) Observed angular distribution, same as in Fig. 2C. (Middle) Simulated polar plots. (Bottom) Simulated 3D probability distribution of the wave packet and their projections onto the three planes.

  • Fig. 5 Time-dependent angular distributions and selected snapshots of unidirectional molecular rotation induced by weaker pulses.

    (A) Observed time- and angular-dependent probability, P(θ = π/2,φ,t). (B) Simulated plot corresponding to (A), with the laser intensity set to 7.5 TW/cm2. (C) Polar plots of the observation in (A).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/1/6/e1400185/DC1

    Fig. S1. Fourier transformation analyses of 〈Pn(cosφ)〉 for the higher-intensity experiment.

    Fig. S2. Time-dependent signal intensity as a measure of the probability in the xy plane.

    Fig. S3. Fourier transformation analyses of 〈Pn(cosφ)〉 for the lower-intensity experiment.

    Movie S1. Unidirectional rotation induced by higher-intensity pulses (all frames of Fig. 3).

    Movie S2. Calculated unidirectional molecular rotation, corresponding to movie S1.

    Movie S3. Experimental movie for the lower-intensity case.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Fourier transformation analyses of 〈Pn(cosϕ)〉 for the higher-intensity experiment.
    • Fig. S2. Time-dependent signal intensity as a measure of the probability in the xy plane.
    • Fig. S3. Fourier transformation analyses of 〈Pn(cosϕ)〉 for the lower-intensity experiment.
    • Legends for movies S1 to S3

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Unidirectional rotation induced by higher-intensity pulses (all frames of Fig. 3).
    • Movie S2 (.mp4 format). Calculated unidirectional molecular rotation, corresponding to movie S1.
    • Movie S3 (.mp4 format). Experimental movie for the lower-intensity case.

    Files in this Data Supplement:

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