High-order harmonic generation by aligned homonuclear diatomic cations

Area of Science:

• Strong-field physics
• Quantum optics
• Molecular physics

Background:

• High-order harmonic generation (HHG) is a key process in nonlinear optics.
• Understanding HHG in molecular systems is crucial for ultrafast science.
• Molecular cations present unique properties compared to neutral molecules.

Purpose of the Study:

• To theoretically investigate high-order harmonic generation in aligned homonuclear diatomic cations.
• To explore the generation of energetic and elliptically polarized harmonics.
• To analyze the potential for producing ultrashort attosecond pulses.

Main Methods:

• Application of the strong-field approximation to a two-center molecular cation model.
• Simulation of harmonic spectra driven by monochromatic and bichromatic laser fields.
• Analysis of harmonic ellipticity as a function of cation orientation and laser polarization.

Main Results:

• Molecular cations allow HHG up to the water-window energy range due to higher ionization potentials.
• Harmonic spectra provide insights into the structure of the highest-occupied molecular orbital.
• An orthogonally polarized two-color field drives the generation of elliptically polarized harmonics.
• Broad regions of high harmonic ellipticity are observed for cations without nodal planes in their orbitals.
• Generation of sub-100 attosecond elliptically polarized pulses is demonstrated.

Conclusions:

• Aligned molecular cations are efficient sources of high-energy harmonics.
• The proposed method enables the generation of tunable, elliptically polarized attosecond pulses.
• Molecular cations offer a promising platform for advanced ultrafast spectroscopy and imaging.