Double core hole valence-to-core x-ray emission spectroscopy: A theoretical exploration using time-dependent density functional theory

Yu Zhang; Uwe Bergmann; Robert Schoenlein; Munira Khalil; Niranjan Govind

doi:10.1063/1.5111141

Double core hole valence-to-core x-ray emission spectroscopy: A theoretical exploration using time-dependent density functional theory

J Chem Phys. 2019 Oct 14;151(14):144114. doi: 10.1063/1.5111141.

Authors

Yu Zhang¹, Uwe Bergmann², Robert Schoenlein³, Munira Khalil⁴, Niranjan Govind⁵

Affiliations

¹ Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
² LCLS and Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
³ SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
⁴ Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
⁵ Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.

PMID: 31615256
DOI: 10.1063/1.5111141

Abstract

With the help of newly developed X-ray free-electron laser (XFEL) sources, creating double core holes (DCHs) simultaneously at the same or different atomic sites in a molecule has now become possible. DCH X-ray emission is a new form of X-ray nonlinear spectroscopy that can be studied with a XFEL. Here, we computationally explore the metal K-edge valence-to-core (VtC) X-ray emission spectroscopy (XES) of metal/metal and metal/ligand DCH states in a series of transition metal complexes with time-dependent density functional theory. The simulated DCH VtC-XES signals are compared with conventional single core hole (SCH) XES signals. The energy shifts and intensity changes of the DCH emission lines with respect to the corresponding SCH-XES features are fingerprints of the coupling between the second core hole and the occupied orbitals around the DCHs that contain important chemical bonding information of the complex. The difference between delocalized/localized core hole models on DCH VtC-XES is also briefly discussed. We theoretically demonstrate that DCH XES provides subtle information on the local electronic structure around metal centers in transition metal complexes beyond conventional linear XES. Our predicted changes from calculations between SCH-XES and DCH-XES features should be detectable with modern XFEL sources.