Tracking Ultrafast Bond Dissociation Dynamics at 0.1 Å Resolution by Femtosecond Extreme Ultraviolet Absorption...

Area of Science:

• Physical Chemistry
• Chemical Physics
• Molecular Dynamics

Background:

• Visualizing real-time chemical bond dissociation requires sub-angstrom spatial and femtosecond temporal resolution.
• Ultrafast molecular dynamics studies face challenges in achieving simultaneous high-resolution measurements.

Purpose of the Study:

• To investigate the C-I bond dissociation dynamics of strong-field-ionized 2-iodopropane (2-C3H7I).
• To develop and apply femtosecond extreme ultraviolet (XUV) absorption spectroscopy for real-time molecular dynamics.
• To achieve sub-100 femtosecond time resolution and sub-angstrom spatial resolution in observing bond dissociation.

Main Methods:

• Femtosecond extreme ultraviolet (XUV) absorption spectroscopy was employed.
• Probing was performed on the iodine 4 d core-level absorption.
• Ab initio calculations were used to determine C-I distance-dependent XUV transition energies.

Main Results:

• A continuous XUV spectral shift was observed on the sub-100 femtosecond timescale during C-I bond dissociation.
• The dissociation of the 2-C3H7I+ spin-orbit-excited state to atomic iodine was resolved.
• Temporal evolution of the C-I distance was reconstructed with 10 fs and 0.1 Å resolution.
• Coupling between C-I bond elongation and coherent vibrational motion of the umbrella mode was identified.

Conclusions:

• Femtosecond XUV absorption spectroscopy, coupled with ab initio simulations, can resolve ultrafast structural dynamics in large polyatomic molecules.
• The study demonstrates the capability of XUV absorption probing to track molecular structural changes with unprecedented resolution.
• The long-range nature of XUV absorption probing was highlighted by its sensitivity to vibrational motion even at extended C-I distances.