Core-electron tunneling in diatomics interacting with intense ultrashort-pulsed XUV and X-ray radiation: Theoretical studies

Abstract

New X-ray free-electron and HHG lasers producing ultra-short pulses of intense XUV/X-ray radiation present a unique opportunity for developing novel techniques which would allow to trace the time evolution of the electronic density in molecular systems and identify signatures of core-electron transitions during the probe pulse. The intensity of XFEL emission is sufficient to influence the field-induced bound-state tunneling of core hole states generated by one-photon ionization. Since molecular imaging experiments at atomic resolution are sensitive to the core-electron density in the target, any density modification has potential implications for the single-shot imaging experiments utilizing femtosecond X-ray pulses. In this work, we discuss the effects of field-induced core-hole transport on X-ray scattering properties in molecular systems. As an example, we consider inter-well tunneling of a core electronic density through the Coulomb barrier between nuclei in a single-electron dicarbon ion under influence of an intense XUV laser field. We employ a simple numerical two-state model which is further corroborated by a numerical solution of the time-dependent three-dimensional Schrödinger equation. Our calculations show pronounced coherent suppression of core-hole delocalization dynamics by very intense XUV laser fields. The laser field parameters determining core-hole tunneling times are scalable for the higher intensity/shorter wavelength regimes. Finally, we discuss the implications of this study for the reconstruction of molecular structures by analysis of scattering data in single-shot XFEL experiments.