Probing electron motion in molecules using strong-field sequential double ionization

Observing electron motion in molecules in the attosecond to femtosecond timescale poses a formidable challenge in ultrafast science. As a superposition of vibronic states is created in the molecule, the vibronic coherence could drive or halt the electron motion, leading to charge migration or charge transfer. Despite these intriguing possibilities, the probing mechanism for such coherence remains elusive. In this talk, we propose to use sequential double ionization (SDI) induced by an intense few-cycle infrared pulse to probe the vibronic coherence. Utilizing a novel density matrix approach[1, 2], we conduct comprehensive simulations of pump-probe experiments on N₂, spanning the entire process. Our findings reveal that the vibronic coherence is remarkably imprinted on the kinetic energy release spectra at different pump-probe delays [3]. Our results establish the theoretical foundation for using SDI to effectively probe vibronic coherence in molecules, marking a significant advancement toward the direct reconstruction of electron motion from experiments.