Transient spectroscopy from time-dependent electronic-structure theory without multipole expansions

Einar Aurbakken*, Benedicte Sverdrup Ofstad, Håkon Emil Kristiansen, Øyvind Sigmundson Schøyen, Simen Kvaal, Lasse Kragh Sørensen, Roland Lindh, Thomas Bondo Pedersen

*Corresponding author for this work

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Abstract

Based on the work done by an electromagnetic field on an atomic or molecular electronic system, a general gauge-invariant formulation of transient absorption spectroscopy is presented within the semiclassical approximation. Avoiding multipole expansions, a computationally viable expression for the spectral response function is derived from the minimal-coupling Hamiltonian of an electronic system interacting with one or more laser pulses described by a source-free, enveloped electromagnetic vector potential. With a fixed-basis expansion of the electronic wave function, the computational cost of simulations of laser-driven electron dynamics beyond the dipole approximation is the same as simulations adopting the dipole approximation. We illustrate the theory by time-dependent configuration interaction and coupled-cluster simulations of core-level absorption and circular dichroism spectra.

Original languageEnglish
Article number013109
JournalPhysical Review A
Volume109
Issue number1
ISSN2469-9926
DOIs
Publication statusPublished - Jan 2024

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© 2024 American Physical Society.

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