A Complete Picture of Electron-Nuclear Coupling Dynamics in H₂⁺

Chemical reactivity is fundamentally governed by the coupled dynamics of electrons and nuclei, which extend beyond the scope of the Born-Oppenheimer approximation. Directly resolving these coupled motions on their intrinsic timescales has remained a significant challenge. We employ a two-color mid-infrared electron-nuclear streaking technique to image electron-nuclear dynamics in real-time. This approach enables the control and tracking of transient electron localization within the hydrogen molecular ion (H₂ ^⁺ ) during its transition from a neutral molecule into an atomic state. We capture the dissociation process of H₂ ^⁺ into two nuclei, revealing the evolution of the quantum tunneling barrier. These findings constitute the first complete electron-nuclear visualization of a photochemical reaction, offering unprecedented insights into molecular dissociation dynamics. This methodology provides a foundation for extending such ultrafast imaging techniques to more complex molecular systems, advancing the understanding of chemical processes at their most fundamental level.