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

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 the ionized water have been studied, the
short-lived intermediate complex and structural dynamic response after the
proton transfer reaction remain poorly understood. Using liquid-phase
ultrafast electron diffraction technique to measure the intermolecular
O··O and O··H 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.