Computation of Partial Auger Decay Widths from Complex-Valued Equation-of-Motion Coupled-Cluster Energies

Area of Science:

• Quantum Chemistry
• Theoretical Spectroscopy
• Computational Physics

Background:

• Auger decay is a fundamental process in atomic and molecular physics.
• Partial Auger decay widths are essential for interpreting Auger spectra but computationally demanding.
• Non-Hermitian quantum mechanics (NHQM) describes decaying states using complex energies.

Purpose of the Study:

• To develop a more efficient method for computing partial Auger decay widths.
• To obtain all partial decay widths simultaneously from a single calculation.
• To validate the new method against existing techniques and apply it to new systems.

Main Methods:

• Utilizing equation-of-motion ionization-potential coupled-cluster (EOMIP-CCSD) theory within non-Hermitian quantum mechanics (NHQM).
• Solving EOMIP-CCSD equations for core-ionized states in the full excitation manifold.
• Decomposing the imaginary part of the complex energy to extract partial decay widths.

Main Results:

• A new computational approach yields partial Auger decay widths efficiently.
• The results closely match those obtained using the Auger channel projectors (ACPs) method.
• Calculated Auger spectra for methane, ethane, hydrogen sulfide, and the cyanide anion (including vibrational broadening).

Conclusions:

• The proposed method provides a computationally advantageous alternative for calculating partial Auger decay widths.
• This technique enables simultaneous determination of all decay channels, simplifying spectral analysis.
• The study presents novel Auger spectra for the cyanide anion, offering insights into core-hole differences.