Autoionization widths by Stieltjes imaging applied to Lanczos pseudospectra.

Area of Science:

• Quantum chemistry
• Atomic and molecular physics
• Computational spectroscopy

Background:

• Autoionization describes electron emission from excited atomic or molecular states above the ionization threshold.
• Fano formalism and Stieltjes imaging are standard methods for calculating autoionization widths from discretized spectra.
• Stieltjes imaging's requirement for full spectra limits its application to large, complex molecular systems.

Purpose of the Study:

• To present a computationally efficient method for calculating autoionization widths.
• To overcome the bottleneck of full diagonalization required by traditional Stieltjes imaging.
• To extend accurate autoionization width calculations to polyatomic systems.

Main Methods:

• Utilizing Lanczos pseudospectra to approximate the full discretized spectrum.
• Adapting a previously developed method for photoionization cross-sections to autoionization width calculations.
• Applying the new method to inner-valence-excited neon, hydrofluoric acid, and benzene.

Main Results:

• Demonstrated that Lanczos pseudospectra can circumvent the need for full diagonalization.
• Successfully calculated autoionization widths for neon, hydrofluoric acid, and benzene using the proposed method.
• Showcased the practicality of the new technique for polyatomic systems.

Conclusions:

• The Lanczos pseudospectra approach provides an efficient alternative to Stieltjes imaging for autoionization width calculations.
• This method significantly reduces computational cost, enabling studies of larger and more complex molecules.
• The technique holds promise for advancing the understanding of autoionizing states in various chemical systems.