Since the advent of femtochemistry, researchers have sought to manipulate chemical processes at the latent length and timescales of atoms and their bonds via coherent control. These experiments have overwhelmingly relied on spectroscopic probes that, while powerful, provide only indirect information on the underlying structural dynamics, leaving a crucial blind spot: the direct, real-space recovery of the atomic and molecular rearrangements in response to coherently controlled excitations. Here, we overcome this limitation by integrating a textbook Tannor-Kosloff-Rice pump-control-probe scheme with ultrafast X-ray scattering to capture snapshots of the wavepacket motion in a benchmark molecular system. We demonstrate this by photoexciting diatomic iodine vapor with a visible pump pulse, selectively steering the wavepacket toward ground-state recombination or dissociative pathways with a time-delayed near-IR control pulse, and recording the dynamics with angstrom and femtosecond precision with an ultrashort hard X-ray probe pulse. By comparing these structural observations with numerical solutions of the time-dependent Schr\"odinger equation, we reveal how coherent control actively reshapes the molecular charge density distribution. Our results pave the way for leveraging structural feedback as a control handle and provide a fundamental microscopic visualization of quantum decoherence and energy redistribution at the atomic level.
Hopper et al. (Mon,) studied this question.