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Journal ArticleDOI

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

TL;DR: 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.

AbstractSeveral 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.

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Citations
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01 Feb 1995
Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

261 citations


Journal ArticleDOI
Abstract: Capturing the evolving geometric and electronic structure in the course of a chemical reaction or biological process is the principal aim of time-resolved X-ray spectroscopies. Recent technological and methodological improvements, such as high repetition rate lasers and femtosecond laser-electron slicing have made this a reality. The advent of X-ray free electron lasers introduces a paradigm shift in terms of the temporal resolution of X-ray spectroscopies, and offer exciting possibilities for time-resolved second-order X-ray spectroscopies and non-linear X-ray experiments. In parallel, the improved data quality is making it increasingly important to accurately simulate the fine spectroscopic details. This has been the driving force for new theoretical methods permitting a detailed interpretation of the spectra in terms of the geometrical and electronic properties of the system. In this contribution, we discuss recent experimental and theoretical developments in ultrafast X-ray absorption spectroscopies (XAS) and explore the new opportunities they offer. (C) 2014 Elsevier B.V. All rights reserved.

163 citations


Journal ArticleDOI
Abstract: After over a decade of development, X-ray transient absorption (XTA) spectroscopy has become an increasingly important and common tool in following molecular structures in chemical reactions and to map out structural factors that could influence reaction pathways. The Perspective reviews current achievements and capabilities in chemical dynamics from XTA spectroscopy based mainly on studies by the authors, collaborators, and cousers of the same facility and then outlines some future challenges and impacts in chemical sciences using pulsed X-rays from the third-generation synchrotron and the fourth-generation X-ray free-electron light sources.

71 citations


Journal ArticleDOI
TL;DR: This work shows how ultrafast hard X-ray pulses may be used to create localized electronic wavepackets in a metalloporphyrin dimer by combining the broad bandwidth of attosecond pulses with the localized nature of core orbitals results in a much higher degree of localization and temporal resolution than is possible with optical pulses.
Abstract: Understanding the excitation energy transfer mechanism in multiporphyrin arrays is key for designing artificial light-harvesting devices and other molecular electronics applications. Simulations of the stimulated X-ray Raman spectroscopy signals of a Zn/Ni porphyrin heterodimer induced by attosecond X-ray pulses show that these signals can directly reveal electron–hole pair motions. These dynamics are visualized by a natural orbital decomposition of the valence electron wavepackets.

39 citations


Journal ArticleDOI
Abstract: Author(s): Bennett, K; Zhang, Y; Kowalewski, M; Hua, W; Mukamel, S | Abstract: New x-ray free electron laser (XFEL) and high harmonic generation (HHG) light sources are capable of generating short and intense pulses that make x-ray nonlinear spectroscopy possible. Multidimensional spectroscopic techniques, which have long been used in the nuclear magnetic resonance, infrared, and optical regimes to probe the electronic structure and nuclear dynamics of molecules by sequences of short pulses with variable delays, can thus be extended to the attosecond x-ray regime. This opens up the possibility of probing core-electronic structure and couplings, the real-time tracking of impulsively created valence-electronic wavepackets and electronic coherences, and monitoring ultrafast processes such as nonadiabatic electron-nuclear dynamics near conical-intersection crossings. We survey various possible types of multidimensional x-ray spectroscopy techniques and demonstrate the novel information they can provide about molecules.

29 citations


Cites background from "Multidimensional X-Ray Spectroscopy..."

  • ...Comparing the 2D signals with different middle probe pulses would bring valuable insights on the complicated many-body interaction of localized excitations [63]....

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  • ...Calculated multidimensional SXRS signals reveal the coupling between various core and valence excitations localized at different x-ray chromorphores in cysteine (figure adapted with permission from [63]....

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References
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Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

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