Journal Article Direct Imaging of Laser-driven Ultrafast Molecular Rotation

水瀬, 賢太  ,  Mizuse, Kenta  ,  藤本, 路夢  ,  Fujimoto, Romu  ,  大島, 康裕  ,  Ohshima, Yasuhiro

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb explosion imaging setup in which a hitherto-impractical camera angle is realized. In our imaging technique, diatomicmolecules are irradiated with a circularly polarized strong laser pulse. The ejected atomic ions are accelerated perpendicularly to the laserpropagation. The ions lying in the laser polarization plane are selected through the use of a mechanical slit and imaged with a high-throughput,2-dimensional detector installed parallel to the polarization plane. Because a circularly polarized (isotropic) Coulomb exploding pulse is used, theobserved angular distribution of the ejected ions directly corresponds to the squared rotational wave function at the time of the pulse irradiation.To create a real-time movie of molecular rotation, the present imaging technique is combined with a femtosecond pump-probe optical setupin which the pump pulses create unidirectionally rotating molecular ensembles. Due to the high image throughput of our detection system, thepump-probe experimental condition can be easily optimized by monitoring a real-time snapshot. As a result, the quality of the observed movieis sufficiently high for visualizing the detailed wave nature of motion. We also note that the present technique can be implemented in existingstandard ion imaging setups, offering a new camera angle or viewpoint for the molecular systems without the need for extensive modification.

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