Are multi-quasiparticle interactions important in molecular ionization?

Area of Science:

• Quantum Chemistry
• Spectroscopy
• Computational Physics

Background:

• Photo-emission spectroscopy reveals electronic states and many-body correlations.
• Accurate theoretical descriptions are needed, especially for complex inner valence excitations.
• The breakdown of the single quasiparticle (QP) picture complicates spectral predictions.

Purpose of the Study:

• To compute and analyze full valence photo-emission spectra for small molecules.
• To compare different many-body perturbation theory methods, including GW and GWΓ.
• To assess the impact of vertex corrections on spectral accuracy.

Main Methods:

• Utilizing the fully correlated adaptive sampling configuration interaction method.
• Employing many-body perturbation theory, specifically GW and vertex-corrected GWΓ (GWΓ) approaches.
• Calculating and comparing full valence spectra across independent and interacting QP regimes.

Main Results:

• GWΓ calculations universally improve theoretical photo-emission spectra for molecular systems.
• Vertex corrections are crucial for accurate QP predictions and satellite structure identification.
• GWΓ provides a unified description across various energy scales.

Conclusions:

• The multi-QP regime in molecular spectra arises from dynamical correlations.
• Perturbation theory, particularly with vertex corrections (GWΓ), accurately describes these correlations.
• GWΓ is essential for precise predictions in computational spectroscopy.