Direct time resolved observation of molecular dynamics induced by soft-x-ray photoionization

We report the first direct observation of ultrafast dynamics in molecules induced by ionizing radiation. We use high harmonic upconversion process to generate soft-x-ray pulses of few femtoseconds duration, which photoionize N₂ molecule. This leads to the formation of highly excited N ₂⁺ ions via inner-shell ionization and electron shakeup processes. We time resolve the unexplored fragmentation dynamics of the electron shakeup states with femtosecond resolution using a strong-field IR probe. The IR pulse promotes the dissociating N₂⁺ wavepacket to repulsive N₂²⁺ potential. We obtain kinetic energy release of N⁺/N⁺ channel as function of time delay and observe a rapid transition from spherically-symmetric molecular potential to a two-center potential within ∼150 fs.