Ultrafast x-ray-induced nuclear dynamics in diatomic molecules using femtosecond x-ray/x-ray pump-probe spectroscopy

Abstract

The capability of generating two intense, femtosecond x-ray pulses with controlled time delay opens the possibility of performing time-resolved experiments for x-ray induced phenomena. We have applied this capability to study the photoinduced dynamics in diatomic molecules. In molecules composed of low-Z elements, \textit{K}-shell ionization creates a core-hole state in which the main decay mode is an Auger process involving two electrons in the valence shell. After Auger decay, the nuclear wavepackets of the transient two-valence-hole states continue evolving on the femtosecond timescale, leading either to separated atomic ions or long-lived quasi-bound states. By using an x-ray pump and an x-ray probe pulse tuned above the \textit{K}-shell ionization threshold of the nitrogen molecule, we are able to observe ion dissociation in progress by measuring the time-dependent kinetic energy releases of different breakup channels. We simulated the measurements on N${}_2$ with a molecular dynamics model that accounts for \textit{K}-shell ionization, Auger decay, and the time evolution of the nuclear wavepackets. In addition to explaining the time-dependent feature in the measured kinetic energy release distributions from the dissociative states, the simulation also reveals the contributions of quasi-bound states.

References in corpus (7)

• Extreme-ultraviolet pump-probe studies of one femtosecond scale electron dynamics
• Catching Conical Intersections in the Act; Monitoring Transient Electronic Coherences by Attosecond Stimulated X-Ray Raman Signals
• Chirped seeded free-electron lasers: self-standing light sources for two-colour pump-probe experiments
• Multiphoton Ionization as a clock to Reveal Molecular Dynamics with Intense Short X-ray Free Electron Laser Pulses
• Nitrogen K-shell photoabsorption
• Two-center Interferences in Photoionization of Dissociating H${}_2^{+}$ Molecule
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• Site-specific Interrogation of an Ionic Chiral Fragment During Photolysis Using an X-ray Free-Electron Laser
• Single-shot MHz velocity-map-imaging using two Timepix3 cameras
• A time-dependent Schrödinger equation for molecular core-hole dynamics
• Auger-induced charge migration
• Normal Auger processes with ultrashort x-ray pulses in Neon
• Revealing and controlling nuclear dynamics following inner-shell photoionization of N2