Intruder Peak-Free Transient Inner-Shell Spectra Using Real-Time Simulations

Area of Science:

• Quantum Chemistry
• Spectroscopy
• Computational Physics

Background:

• Real-time methods offer convenience for simulating core-level absorption spectra.
• Atom-centered basis sets in these methods can introduce nonphysical intruder peaks.
• These peaks exhibit unphysical time-dependent modulations in energy and oscillator strength for transient absorption spectra.

Purpose of the Study:

• To investigate the origins of intruder peaks in real-time simulated absorption spectra.
• To propose and validate a straightforward solution for removing these nonphysical artifacts.
• To enable accurate computation of intruder-free attosecond transient X-ray absorption spectra.

Main Methods:

• Utilized real-time time-dependent density functional theory (RT-TDDFT).
• Developed and applied a filtered dipole operator.
• Computed spectra for aminophenol (C6H7NO) at oxygen and nitrogen K-edges and α-quartz (SiO2) at the silicon L-edge.

Main Results:

• Demonstrated that the filtered dipole operator effectively eliminates intruder peaks.
• Showcased the computation of intruder-free attosecond transient X-ray absorption spectra.
• Highlighted that unfiltered spectra were qualitatively incorrect.

Conclusions:

• The filtered dipole operator provides a straightforward and effective solution to intruder peaks in RT-TDDFT.
• This method is crucial for obtaining accurate static and transient inner-shell spectroscopy results.
• The approach is readily implementable in various real-time simulation methodologies.