Single and sequential double ionization of NO radical in intense laser fields

Area of Science:

• Atomic and Molecular Physics
• Quantum Chemistry
• Laser-Induced Dynamics

Background:

• Understanding molecular ionization dynamics in intense laser fields is crucial for controlling chemical reactions.
• Nitric oxide (NO) is a fundamental diatomic molecule with a complex electronic structure, making it an interesting subject for ionization studies.

Purpose of the Study:

• To investigate the angular dependence of single and double ionization probabilities of NO in an intense laser field.
• To elucidate the role of molecular orbitals and electronic states in the ionization process.

Main Methods:

• Experimental setup using a 790 nm, 100 fs laser at intensities of 1-10 × 10^14 W/cm^2.
• Theoretical analysis employing the molecular Ammosov-Delone-Krainov (MO-ADK) theory.
• Consideration of the time evolution of electron density distribution in molecular orbitals.

Main Results:

• Double ionization probability of NO is enhanced when the molecular axis is parallel to the laser polarization.
• Angular dependence of sequential double ionization is linked to the 5σ orbital of NO+.
• Fast oscillations in tunnel ionization probability are well-described by MO-ADK theory, accounting for spin-orbit coupling and electron density dynamics.

Conclusions:

• The orientation of the NO molecule relative to the laser polarization significantly influences its ionization pathways.
• Molecular orbital structure, particularly the 5σ orbital, dictates the angular distribution of double ionization.
• Advanced theoretical models like MO-ADK are effective in describing complex ionization phenomena in molecules.