Electron and fluorescence spectra of a water molecule irradiated by an x-ray free-electron laser pulse

Julia M. Schäfer, Ludger Inhester, Sang-Kil Son, Reinhold F. Fink, and Robin Santra

Phys. Rev. A 97, 053415 – Published 29 May 2018

Abstract

With the highly intense x-ray light generated by x-ray free-electron lasers (XFELs), molecular samples can be ionized many times in a single pulse. Here we report on a computational study of molecular spectroscopy at the high x-ray intensity provided by XFELs. Calculated photoelectron, Auger electron, and x-ray fluorescence spectra are presented for a single water molecule that reaches many electronic hole configurations through repeated ionization steps. The rich details shown in the spectra depend on the x-ray pulse parameters in a nonintuitive way. We discuss how the observed trends can be explained by the competition of microscopic electronic transition processes. A detailed comparison between spectra calculated within the independent-atom model and within the molecular-orbital framework highlights the chemical sensitivity of the spectral lines of multiple-hole configurations. Our results demonstrate how x-ray multiphoton ionization-related effects such as charge-rearrangement-enhanced x-ray ionization of molecules and frustrated absorption manifest themselves in the electron and fluorescence spectra.

Received 22 February 2018

DOI:https://doi.org/10.1103/PhysRevA.97.053415

Physics Subject Headings (PhySH)

Autoionization & Auger processes Laser spectroscopy Molecular spectra Multiphoton or tunneling ionization & excitation Photoemission Ultrafast phenomena

Atomic, Molecular & Optical

Authors & Affiliations

Julia M. Schäfer^1,2,*, Ludger Inhester^1,†, Sang-Kil Son^1,‡, Reinhold F. Fink^2,§, and Robin Santra^1,3,∥

¹Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg, Germany
²Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
³Department of Physics, University of Hamburg, Jungiusstrasse 9, 20355 Hamburg, Germany

^*julia.schaefer@cfel.de
^†ludger.inhester@cfel.de
^‡sangkil.son@cfel.de
^§reinhold.fink@uni-tuebingen.de
^∥robin.santra@cfel.de

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Vol. 97, Iss. 5 — May 2018

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