美国国家加速器实验室X. J. Wang团队报道了电离液态水中短寿命羟基离子对的成像。相关研究成果于2021年10月1日发表于国际一流学术期刊《科学》。

水的辐解在自然界中无处不在，在许多生化和技术应用中起着关键作用。虽然电离水的基本反应途径已经被研究，但其质子转移反应后的短寿命中间络合物和结构动力学响应仍然知之甚少。

使用液相超快电子衍射技术测量分子间氧··氧和氧··氢键，研究人员捕获了在140飞秒内通过直接氧··氧键收缩和质子转移形成的短寿命自由基阳离子络合物OH（H₃O⁺），然后是自由基-阳离子对的解离和随后在250飞秒内水的结构弛豫。以上测量提供了在分离前捕获这种亚稳自由基-阳离子络合物的直接证据，从而提高了人们对电离液态水中基本反应动力学的基本理解。

附：英文原文

Title: Imaging the short-lived hydroxyl-hydronium pair in ionized liquid water

Author: M.-F. Lin, N. Singh, S. Liang, M. Mo, J. P. F. Nunes, K. Ledbetter, J. Yang, M. Kozina, S. Weathersby, X. Shen, A. A. Cordones, T. J. A. Wolf, C. D. Pemmaraju, M. Ihme, X. J. Wang

Issue&Volume: 2021-10-01

Abstract: The radiolysis of water is ubiquitous in nature and plays a critical role in numerous biochemical and technological applications. Although the elementary reaction pathways for ionized water have been studied, the short-lived intermediate complex and structural dynamic response after the proton transfer reaction remain poorly understood. Using a liquid-phase ultrafast electron diffraction technique to measure the intermolecular oxygen···oxygen and oxygen···hydrogen bonds, we captured the short-lived radical-cation complex OH(H3O+) that was formed within 140 femtoseconds through a direct oxygen···oxygen bond contraction and proton transfer, followed by the radical-cation pair dissociation and the subsequent structural relaxation of water within 250 femtoseconds. These measurements provide direct evidence of capturing this metastable radical-cation complex before separation, thereby improving our fundamental understanding of elementary reaction dynamics in ionized liquid water.

DOI: abg3091

Source: https://www.science.org/doi/10.1126/science.abg3091