Japan High Energy Accelerator Research Institute (KEK), the University of Tokyo, Ritsumeikan University, Chiba University, Kyoto University, Quantum Science and Technology Research and Development Institute (QST), the Institute of Physics and Chemistry (RIKEN), and the High Brightness Optical Science Research Center (JASRI) The joint research team announced on December 12, 2016 that the femtosecond X-ray photoelectron diffraction method was used to successfully determine the structure of the iodine molecule in the infrared pulsed intense laser electric field.
For gas phase molecules oriented in random directions, the information on the direction of photoelectron release is easily averaged in the direction of the molecule, and photoelectron diffraction images cannot be obtained. Therefore, in this experiment, a YAG laser pointer was irradiated to iodine molecules (I2) in the gas phase, and the direction of I2 was unified by the electric field of the laser. After that, the XFEL pulse that completely overlaps the YAG laser in time and space was irradiated, and the X-ray photoelectron diffraction image of the I 2p orbital released from the iodine atom (I) in I 2 was detected.
In order to establish the structure (atomic distance) of I2 in the YAG laser electric field, the research team compared the measured photoelectron diffraction image with the calculation result of the photoelectron diffraction theory that uses the ionization energy of the I 2p orbital and the atomic distance as parameters. Then a two-dimensional graph is used to show the difference between the experimental results and the theoretical results. The results show that the interatomic distance of I2 in the YAG laser electric field becomes weaker under the action of the laser electric field, so it is longer than the interatomic distance of the balanced structure of I2 10%, which is 0.2 to 0.3 angstroms (10-10m).
Although the infrared pulse YAG green laser pointer is used this time, it is expected that ultra-high-speed photochemical reactions can be visualized by introducing short-pulse pump lasers that excite photochemical reactions. This achievement makes the ultimate visualization of photochemical reactions in time and space “Molecular Movie” a big step forward. In the future, the goal of the research team is to use femtosecond X-ray photoelectron diffraction to identify ultra-high-speed molecules. The kinetics of photochemical reactions and the exploration of reaction control methods. The results of this research have been published in the online scientific journal “Science Reports.”