Relativistic time-dependent configuration-interaction singles

TL;DR

This paper introduces and implements a relativistic time-dependent configuration interaction singles (RTDCIS) method, comparing its results with experimental data and other theoretical approaches for noble gas atoms, enabling future studies of relativistic strong-field phenomena.

Contribution

The paper presents the derivation and implementation of the RTDCIS method, including validation and benchmarking against experimental and theoretical data, facilitating advanced relativistic atomic simulations.

Findings

RTDCIS accurately reproduces experimental energies and cross sections.

Excellent agreement with relativistic random phase approximation benchmarks.

Validation of complex absorbing potential for photoelectron removal.

Abstract

In this work, a derivation and implementation of the relativistic time-dependent configuration interaction singles (RTDCIS) method is presented. Various observables for krypton and xenon atoms obtained by RTDCIS are compared with experimental data and alternative relativistic calculations. This includes energies of occupied orbitals in the Dirac-Fock ground state, Rydberg state energies, Fano resonances and photoionization cross sections. Diagrammatic many-body perturbation theory, based on the relativistic random phase approximation, is used as a benchmark with excellent agreement between RTDCIS reported at the Tamm-Dancoff level. Results from RTDCIS are computed in the length gauge, here the negative energy states can be omitted with acceptable loss of accuracy. A complex absorbing potential, that is used to remove photoelectrons far from the ion, is implemented as a scalar potential and validated for RTDCIS. The RTDCIS methodology presented here opens for future studies of strong-field processes, such as attosecond transient absorption and high-order harmonic generation, with electron and hole spin dynamics and other relativistic effects described by first principle via the Dirac equation.