Multidimensional X-Ray Spectroscopy of Valence and Core Excitations in Cysteine

TL;DR

This paper simulates multidimensional x-ray spectroscopy experiments on cysteine, revealing how 2D and 3D signals can provide detailed insights into core-valence excitations and their couplings.

Contribution

It introduces a simulation framework for multidimensional x-ray spectroscopy of cysteine, highlighting the potential of 3D signals to visualize core-valence couplings.

Findings

3D plots reveal core-valence excitation couplings

Four-pulse signals provide new insights into SXRS

Simulations demonstrate detailed visualization of excitation origins

Abstract

Several nonlinear spectroscopy experiments which employ broadband x-ray pulses to probe the coupling between localized core and delocalized valence excitation are simulated for the amino acid cysteine at the K-edges of oxygen and nitrogen and the K and L-edges of sulfur. We focus on two dimensional (2D) and 3D signals generated by two- and three-pulse stimulated x-ray Raman spectroscopy (SXRS) with frequency-dispersed probe. We show how the four-pulse x-ray signals $\boldsymbol{k}_\mathrm{I}=-\boldsymbol{k}_1+\boldsymbol{k}_2+\boldsymbol{k}_3$ and $\boldsymbol{k}_\mathrm{II}=\boldsymbol{k}_1-\boldsymbol{k}_2+\boldsymbol{k}_3$ can give new 3D insight into the SXRS signals. The coupling between valence- and core-excited states can be visualized in three dimensional plots, revealing the origin of the polarizability that controls the simpler pump-probe SXRS signals.