Ultrafast Electron–Dipole Interactions in TeO ^– Photodetachment

We present direct experimental evidence of ultrafast coupling between ejected electrons and dynamically forming dipole moments in TeO, captured during the photodetachment of TeO^-. By combining high-resolution cryogenic photoelectron spectroscopy with velocity-map imaging, we assess previously inaccessible excited states and resolve rich photoelectron angular distributions (PADs) that encode electron-dipole interactions. Systematic comparison of PADs from femtosecond and picosecond lasers reveals striking deviations from free-electron behavior, representing direct evidence of a transient dipole moment evolving on femtosecond time scales. Quantitative analysis pinpoints the dipole buildup time to be within ∼60 fs, providing real-time access to the birth of a molecular dipole field. This work establishes a general approach to probing electron-dipole interactions in their formation stages, offering fundamental insights into the ultrafast interplay between departing electrons and transient polar systems─a process that lies at the core of atomic, molecular, and ultrafast physics.