Time-resolved intramolecular photoelectron scattering

When a molecule is ionized by an x-ray photon from a localized core orbital, the emerging photoelectron collides with nearby nuclei giving rise to the well-known interference pattern of EXAFS spectroscopy. The vibrationally-resolved spectrum of core-ionized molecules bears the signature of the energy transferred to the nuclei by the intramolecular scattering process [1,2]. New pulsed x-ray sources, such as XFELS, make it now possible to study this phenomenon resolved in time. In this work, we simulate the real-time dynamics of the CO molecule following the C-1s ionization induced by a coherent soft-x-ray pulse using a simplified 1D analytical model that captures the essential aspects of the process. The vibrationally-resolved photoemission delay bears the signature of electron localization at birth as well as of its resonant confinement by the two nuclei. For short pulses, the ion is created in a partially coherent vibrational state: either in compression or in expansion, depending on the pulse central energy with respect to the nearest confinment resonance. The deviation of the nuclear Wigner distribution maximum from the sudden photoemission expectation value can be interpreted as a vibrational delay due to intramolecular scattering. 

[1] E. Plésiat et al., Phys. Rev. A 85, 023409 (2012)

[2] K. Ueda et al., J. Chem. Phys. 139, 124306 (2013)