Communication: Tracking molecular structure deformation and relaxation in real time

Area of Science:

• Physical Chemistry
• Molecular Dynamics
• Spectroscopy

Background:

• Understanding molecular structural dynamics under intense laser fields is crucial for controlling chemical reactions.
• Methyl iodide (CH3I) serves as a model system for studying light-induced molecular transformations.

Purpose of the Study:

• To investigate the ultrafast structural deformation of CH3I induced by strong femtosecond laser fields.
• To characterize the temporal evolution of molecular structure using time- and frequency-resolved ro-vibrational spectroscopy.

Main Methods:

• Utilizing time- and frequency-resolved ro-vibrational spectroscopy.
• Applying intense femtosecond laser fields (greater than 10^11 W/cm^2) to induce molecular excitation.

Main Results:

• Observed ultrafast "umbrella-closing" structural deformation of the CH3 group in CH3I.
• Characterized a subsequent "umbrella-opening" structural relaxation with an exponential decay time of approximately 620 fs.

Conclusions:

• Demonstrated the capability of time- and frequency-resolved vibrational spectra to probe ultrafast molecular deformation dynamics.
• Provided insights into the transient structural changes of CH3I under strong laser irradiation.