Time-resolved electron spin resonance spectroscopy of integer-spin reaction intermediates using terahertz waves

2023 Fiscal Year Final Research Report

• Project/Area Number: 21H01040
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Kobe University
• Principal Investigator: Ohmichi Eiji 神戸大学, 理学研究科, 准教授 (00323634)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 電子スピン共鳴 / テラヘルツ波 / 時間分解測定 / 反応中間体

Outline of Final Research Achievements

In order to establish a novel technique for time-resolved electron spin resonance (ESR) spectroscopy in the terahertz (THz) region, we developed the THz-ESR measurement system combined with a nanosecond pulse laser. Finally, the system with a time resolution of 10 ns was developed at cryogenic temperatures. Also, in order to increase the sensitivity, we fabricated metallic planar antennas to enhance the oscillating magnetic field components of THz waves. According to the numerical simulations, a 100-fold increase of the oscillating magnetic field was attained in a wide frequency range. We paid attention to the interaction between ferrous irons (S=2) and the amyloid β protein, which is thought to be responsible for the emergence of Alzheimer diseases. Preliminary X-band ESR measurements are suggestive of the important role of integer spins in the interactions between iron ions and amyloid β.

Free Research Field

固体物理

Academic Significance and Societal Importance of the Research Achievements

時間分解電子スピン共鳴法はマイクロ秒の時間分解能で短寿命反応中間体を捕捉できる優れた分光法である。しかし、従来法ではXバンド帯で測定を行っていることからゼロ磁場分裂と呼ばれるエネルギーギャップを持つような整数スピン状態に対しては測定が不可能であった。しかし、多くの遷移金属イオン（Cr4+、Mn3+、Fe4+、Fe2+、Ni2+）では整数スピン状態をとり、触媒・酵素反応において極めて重要な役割を担っていることが知られている。本研究により未開拓であった遷移金属イオンの時間分解電子スピン共鳴測定が可能になれば光触媒反応や金属タンパク質酵素反応の反応機構解明に向けた手掛かりを得ることが可能になる。