AsianScientist (Jul. 14, 2015) – Researchers have developed a technique that allows them to visualize subnano-scale molecules making a hundred billion rotations per second. Their results have been published in Science Advances.
The research team led by Professor Yasuhiro Ohshima at the Tokyo Institute of Technology, and Dr. Kenta Mizuse at the Institute for Molecular Science, National Institutes of Natural Sciences, successfully took sequential ‘snapshots’ of ultrafast unidirectionally rotating molecules of nitrogen using their newly developed Coulomb explosion imaging setup.
Rotational wave packets (RWPs) are time-varying states of motion of rotating microscopic objects like molecules that change shape in an ultrafast time scale—typically in a trillionth of a second. More importantly, because RWPs are governed by quantum mechanics, they show a wave-like nature, behaving differently from macroscopic objects. RWPs are thus an ideal candidate for examining the connection between quantum and classical worlds.
In the present study, the RWPs were created by using a pair of ultrafast laser pulses which had their mutual delay and polarization properly adjusted. To visualize the ultrafast molecular rotations, the team developed a Coulomb explosion imaging setup by regulating the rotational direction by a pair of time-delayed, polarization-skewed laser pulses.
The team successfully recorded a series of images of time-varying molecular angular distribution with high-spatial resolution, stitching the sequential ‘snapshots’ together to form a movie which showed the wave-like nature of the RWPs.
Multiple running waves were shown to gather, giving a highly concentrated spatial orientation that subsequently split into parts having different angular velocities, while the overall movement kept rotating in one direction. Furthermore, the team obtained images of unidirectional RWPs at a viewing angle that the previous 2D imaging studies could not adopt.
There have been many proposals for novel application of unidirectional RWPs. For instance, unidirectionally rotating molecular gas ensembles are expected to make sophisticated polarization shaping of ultrafast light pulses. In addition, unidirectional RWPs exhibiting cogwheel-like motion are expected to be used as a ‘stopwatch’ to measure the precise time difference between pulses from two independent ultrafast laser systems.
“We hope our high-resolution RWP imaging to be applicable in making a movie on such crossovers from quantum to classical worlds,” Ohshima said.
The article can be found at: Mizuse et al. (2015) Quantum Unidirectional Rotation Directly Imaged with Molecules.
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Source: National Institutes of Natural Sciences.
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