Implementation and validation of the relativistic transient absorption theory within the dipole approximation

TL;DR

This paper develops and validates a relativistic transient absorption theory using the Dirac equation within the dipole approximation, enabling more accurate studies of heavy atoms and relativistic effects in attosecond spectroscopy.

Contribution

It introduces a novel relativistic transient absorption framework derived from the Dirac equation and validates it through simulations, advancing the methodology for studying relativistic phenomena in attosecond physics.

Findings

Validation of the relativistic theory through simulations

Potential to study relativistic effects like Zitterbewegung

Foundation for a more general relativistic spectroscopy method

Abstract

A relativistic transient absorption theory is derived, implemented and validated within the dipole approximation based on the time-dependent Dirac equation. Time-dependent simulations have been performed using the Dirac equation and the Schr\"odinger equation for the Hydrogen atom in two different attosecond transient absorption scenarios. These simulations validate the present relativistic theory. The presented work can be seen as a first step in the development of a more general relativistic attosecond transient absorption spectroscopy method for studying heavy atoms, but it also suggests the possibility of studying relativistic effects, such as Zitterbewegung, in the time domain.