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

• Published in: Science (American Association for the Advancement of Science) Vol. 374; no. 6563; pp. 92 - 95
• Main Authors: Lin, M-F, Singh, N, Liang, S, Mo, M, Nunes, J P F, Ledbetter, K, Yang, J, Kozina, M, Weathersby, S, Shen, X, Cordones, A A, Wolf, T J A, Pemmaraju, C D, Ihme, M, Wang, X J
• Format: Journal Article
• Language: English
• Published: United States The American Association for the Advancement of Science 01-10-2021; AAAS
• Subjects: Cations; Dynamic response; Electron diffraction; Hydrogen bonding; Hydrogen bonds; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Ionization; Ionizing radiation; Liquid phases; Oxygen; Protons; Radiolysis; Water
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.abg3091

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(H
O
) 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.