Control of surface chemical reactions by a monocycle THz pulse

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K15226
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 32010:Fundamental physical chemistry-related
• Research Institution: The University of Tokyo
• Principal Investigator: Tanaka Shunsuke 東京大学, 物性研究所, 助教 (10822744)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: THz-induced reactions / TFISH / metal surface / Gapless THz detection

Outline of Final Research Achievements

We prepared well-defined surfaces such as Cs/Pt and O+CO/Pt under ultrahigh vacuum conditions, and the surfaces were irradiated by monocycle THz pulses with the maximum electric field of 183 kV/cm to investigate whether chemical reactions could be induced by the THz pulses. Although we tried to detect desorbed species by a quadrupole mass spectrometer, and measure the displacement of the adsorbed species by second harmonic generation spectroscopy or sum frequency generation spectroscopy, we could not observe neither the displacement of the adsorbed species nor the THz pulse-induced chemical reactions. Thus, we concluded that THz pulses with a stronger electric field are necessary to induce the chemical reactions.
In the above research, we could develop a new method to observe the waveform of THz pulses by using second harmonic lights from metal surfaces.

Free Research Field

表面非線形分光

Academic Significance and Societal Importance of the Research Achievements

私はair-metal-coherent-detection(AMCD)というTHzパルス検出方法を開発した。この方法は、THz電場が誘起する空気分子からの第二高調波光と金属表面からの第二高調波光の干渉を利用する。THz電場が作用する対象が空気分子であるため、AMCDは広帯域THzパルスのギャップレス検出を可能にする。広帯域THzパルス光の検出方法として、air-biased-coherent-detection(ABCD)が有名であるが、ABCDに比べて、AMCDは空気分子と金属薄膜だけでよい。その簡便性から、AMCDは広帯域THzパルスの時間波形計測方法の一つとして普及するものと考える。