Polyatomic molecules under intense femtosecond laser irradiation

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Chemistry
• Physical Chemistry

Background:

• Strong-field laser-matter interactions are crucial for advanced techniques like attosecond pulse generation.
• While atomic behavior in intense fields is understood, molecular responses remain less clear, with current models showing limitations.
• Molecules exhibit complex nuclear and electronic motions, making them distinct from atoms in strong laser fields.

Purpose of the Study:

• To investigate the extent to which molecules retain their identity and properties under intense femtosecond laser fields.
• To explore the structure-sensitive dynamics and fragmentation patterns of aryl alkyl ketones.
• To develop and validate a model for strong-field ionization and fragmentation in polyatomic molecules.

Main Methods:

• Experimental investigation using time-of-flight mass spectrometry and pump-probe techniques.
• Theoretical calculations including high-level ab initio quantum chemistry.
• Analysis of ion yield modulation and molecular dynamics under intense laser irradiation.

Main Results:

• Positional isomers showed distinct dynamical behaviors influenced by minor energy variations (meV) under high fields (V/Å).
• A proposed model describes ionization occurring on a suboptical cycle timescale, followed by fragmentation via photon absorption.
• Experimental results align with the hypothesis that photoelectron loss outpaces intramolecular vibrational relaxation.

Conclusions:

• Molecular identity and dynamics are significantly influenced by subtle structural differences even under extreme laser conditions.
• The proposed ionization-fragmentation model provides a framework for understanding polyatomic molecule behavior in strong fields.
• Findings contribute to the advancement of laser-driven molecular science and control.