Probing orbital structure of polyatomic molecules by high-order harmonic generation.

Area of Science:

• Quantum optics
• Molecular physics
• Attosecond science

Background:

• High-order harmonic generation (HHG) is a key process in strong-field physics.
• Understanding molecular electronic structure is crucial for controlling chemical reactions.
• Laser-induced alignment offers a way to probe molecular properties with high resolution.

Purpose of the Study:

• To investigate the influence of electronic structure and symmetry on HHG in aligned polyatomic molecules.
• To demonstrate the capability of HHG as a tool for imaging molecular orbitals in larger systems.
• To validate theoretical models like the strong-field approximation for complex molecules.

Main Methods:

• Utilizing laser-aligned conjugated polyatomic molecular systems (acetylene and allene).
• Analyzing the angular dependence of harmonic yield relative to the driving laser field polarization.
• Comparing experimental results with theoretical calculations based on the strong-field approximation.

Main Results:

• Observed clear signatures of highest occupied molecular orbitals in the harmonic yield's angular dependence.
• Achieved good quantitative agreement between experimental data and theoretical predictions.
• Demonstrated that HHG reflects the electronic structure of molecules like acetylene and allene.

Conclusions:

• Electronic structure and symmetry significantly impact HHG in aligned molecules.
• Molecular orbital imaging techniques can be extended to larger, polyatomic systems.
• HHG is a powerful method for probing and understanding the electronic properties of complex molecules.