Accurate Relativistic Real-Time Time-Dependent Density Functional Theory for Valence and Core Attosecond Transient...

Area of Science:

• Quantum Chemistry
• Theoretical Spectroscopy
• Computational Physics

Background:

• Simulating out-of-equilibrium electron dynamics in attosecond pump-probe transient absorption spectroscopy (TAS) is challenging, particularly for heavy elements and core excitations.
• Relativistic effects, including scalar and spin-orbit interactions, are crucial for accurately describing these processes but computationally demanding.

Purpose of the Study:

• To develop a robust theoretical methodology for simulating TAS that incorporates relativistic effects.
• To enable accurate modeling of both valence and core electron dynamics in TAS experiments.
• To provide a computationally efficient approach for relativistic TAS simulations.

Main Methods:

• Formulation of a relativistic real-time, time-dependent density functional theory (RT-TDDFT) framework for TAS.
• Implementation of a full four-component (4c) RT-TDDFT approach.
• Introduction of the atomic mean-field exact two-component (amfX2C) Hamiltonian as a computationally efficient alternative to 4c calculations.
• Application of relativistic nonequilibrium response theory.

Main Results:

• The developed methodology successfully simulates valence and near-L2,3-edge TAS processes.
• The amfX2C approach offers a significant reduction in computational cost while maintaining the accuracy of the 4c method.
• The study provides new physical insights into relativistic electron dynamics during TAS.

Conclusions:

• The new relativistic RT-TDDFT methodology, including the amfX2C approximation, is a powerful tool for studying attosecond pump-probe transient absorption spectroscopy.
• This approach enables accurate and efficient theoretical modeling of complex electron dynamics involving relativistic effects.
• The findings will aid in the interpretation of experimental TAS data and guide future research in ultrafast spectroscopy.