Dr. Yasuhiro Ohshima

Abstract

In a gas-phase ensemble at room temperature, molecules are, in an average, flying away by a few hundred meters, making turns almost reaching to 10¹¹ times, and shaking themselves more than 10¹³ times within the duration of only one second. One of the ultimate goals for chemists is to capture the lively figures of molecules moving in such a dynamic manner and to have a perfect command over the molecular motions.

When a gaseous molecular sample is irradiated by an intense nonresonant ultrashort laser pulse, rotation of the molecules is coherently excited to form nonstationary quantum states of motion, i.e., quantum wave packets [1]. We designed and constructed a new 2D ion-imaging apparatus [2], which allows us to track the spatiotemporal propagation of coherent rotation of molecules as a series of time-dependent molecular orientational distribution [3]. Some of such “molecular movies” will be shown in my talk. Wave-packet imaging will also be utilized as a new approach in molecular spectroscopy. Rotational spectra have been successfully extracted for molecular clusters of nonpolar molecules [4,5], to reveal the geometry and internal dynamics of the systems to be studied. In addition, it will be shown that even molecular vibration is captured in the time-dependent ion images.

[1] Y. Ohshima and H. Hasegawa, Int. Rev. Phys. Chem. 29, 619 (2010)

[2] K. Mizuse, R. Fujimoto, and Y. Ohshima, Rev. Sci. Instrum. 90, 103107 (2019).

[3] K. Mizuse, K. Kitano, H. Hasegawa, and Y. Ohshima, Sci. Adv. 1, e1400185 (2015).

[4] K. Mizuse, U. Sato, Y. Tobata, and Y. Ohshima, Phys. Chem. Chem. Phys. 24, 11014 (2022).

[5] K. Mizuse, K. Takano, E. Kakizaki, Y. Tobata, and Y. Ohshima, J. Phys. Chem. A 127, 4848 (2023).

Faculty Webpage

https://www.irfi.titech.ac.jp/wrhi-archive/en/people/yasuhiro-ohshima/index.html