Time-resolving state-specific molecular dissociation with XUV broadband absorption spectroscopy

Area of Science:

• Chemical Physics
• Molecular Dynamics
• Spectroscopy

Background:

• Molecular electronic and nuclear dynamics govern chemical reactions on ultrafast timescales.
• Free-electron lasers (FELs) provide femtosecond resolution and selectivity for studying molecular dynamics.
• Current time-resolved methods struggle with neutral fragments or limited spectral bandwidth.

Purpose of the Study:

• To develop and demonstrate a novel time-resolved technique for observing molecular dissociation pathways.
• To investigate competing dissociation channels of specific molecular states.
• To overcome limitations of existing methods in detecting neutral fragments and spectral bandwidth.

Main Methods:

• Combining broadband extreme ultraviolet (XUV) probe pulses with FEL pump pulses.
• Utilizing high-order harmonic generation for broadband XUV generation.
• Measuring resonances of ionic and neutral fragments to resolve dissociation dynamics.

Main Results:

• Temporally resolved the dissociation of a specific O₂⁺ state into two competing pathways.
• Successfully detected both ionic and neutral fragments, providing a complete picture of dissociation.
• Demonstrated the capability to observe dynamics on ultrafast timescales with high selectivity.

Conclusions:

• The combined XUV probe and FEL pump scheme enables comprehensive studies of molecular dissociation.
• This method advances the understanding of ultrafast chemical dynamics and quantum state-resolved fragment detection.
• The technique is applicable to complex dynamics in larger molecules across various scientific fields.