Abstract
We propose a general theoretical scheme of relativistic electron-nucleus coupled dynamics of molecules in radiation fields, which is derived from quantum electrodynamical formalism. Aiming at applications to field-induced dynamics in ultrastrong laser pulses to the magnitude of 1016 W/cm2 or even larger, we derive a nonperturbative formulation of relativistic dynamics using the Tamm-Dancoff expansion scheme, which results in, within the lowest order expansion, a time-dependent Schrödinger equation with the Coulombic and retarded transversal photon-exchange interactions. We also discuss a wavepacket type nuclear dynamics adapted for such dynamics.
Highlights
Relativistic electrons appear in orbitals of heavy atoms where it has been established that the inner-shell electrons[5,6,7] and valence electrons are subject to relativistic effects such as the orbital contraction/expansion effects.[8,9]
We have developed a nonperturbative approach for relativistic electron-nucleus coupled dynamics
We consider that this approach has potential applications to the electron dynamics induced by ultraintense IR laser fields
Summary
Electrons accelerated close to the speed of light exhibit relativistic effects.[1,2,3,4] In molecular science, relativistic electrons appear in orbitals of heavy atoms where it has been established that the inner-shell electrons[5,6,7] and valence electrons are subject to relativistic effects such as the orbital contraction/expansion effects.[8,9] Another important type of relativistic electrons in molecular science is those accelerated in ultraintense optical fields.[10,11] The former aspect has been discussed separately in our recent work[12] within the path integral formalism. In Ref. 20, CH4 molecules irradiated by IR laser fields of intensity exceeding 1016 W/cm[2] were observed to undergo multiple tunnel ionizations, followed by rapid fragmentation.[20] Such dynamics is challenging in that strong electron-radiation coupling does not allow perturbative approach which is the most standard tool in the quantum electrodynamics (QED). One of the main objectives in this paper is to extend such non-BO wavepacket dynamics to the relativistic regime Another shortcoming of the conventional type of relativistic quantum chemistry is that it often shows lack of theoretical rigor; predominantly many of those studies have been made based on the Dirac-Coulomb or the Dirac-Breit theory, which are the low-energy static reductions of the exact QED.
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