Double-quantum-coherence attosecond x-ray spectroscopy of spatially separated, spectrally overlapping core-electron transitions

TL;DR

This paper demonstrates how double-quantum-coherence attosecond x-ray spectroscopy can probe couplings between core-electron transitions, revealing molecular structure details beyond traditional XANES methods.

Contribution

It introduces a simulation approach for 2DXCS signals that detect couplings between spatially-separated core-electron transitions, providing new insights into molecular geometry.

Findings

2DXCS signals are background-free and sensitive to core-electron couplings.

Features reveal couplings between core transitions connected by valence excitations.

Method offers information on molecular structure not accessible by linear XANES.

Abstract

X-ray four-wave mixing signals generated in the $k_1 + k_2 - k_3$ phase-matching direction are simulated for N1s transitions in para-nitroanline and two-ring hydrocarbons disubstituted with an amine and a nitroso groups. The two-dimensional x-ray correlation spectra (2DXCS) provide background-free probes of couplings between core-electron transitions even for multiple core shells of the same type. Features attributed to couplings between spatially-separated core transitions connected by delocalized valence excitations provide information about molecular geometry and electronic structure unavailable from linear near-edge x-ray absorption (XANES).