Alternative difference analysis scheme combiningR-space EXAFS fit with global optimization XANES fit for X-ray transient absorption spectroscopy

Time-resolved X-ray absorption spectroscopy (TR-XAS), based on the laser-pump/X-ray-probe method, is powerful in capturing the change of the geometrical and electronic structure of the absorbing atom upon excitation. TR-XAS data analysis is generally performed on the laser-on minus laser-off difference spectrum. Here, a new analysis scheme is presented for the TR-XAS difference fitting in both the extended X-ray absorption fine-structure (EXAFS) and the X-ray absorption near-edge structure (XANES) regions.R-space EXAFS difference fitting could quickly provide the main quantitative structure change of the first shell. The XANES fitting part introduces a global non-derivative optimization algorithm and optimizes the local structure change in a flexible way where both the core XAS calculation package and the search method in the fitting shell are changeable. The scheme was applied to the TR-XAS difference analysis of Fe(phen)3spin crossover complex and yielded reliable distance change and excitation population.

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Tracking the Metal-Centered Triplet in Photoinduced Spin Crossover of Fe(phen)32+ with Tabletop Femtosecond M-edge XANES

10.26434/chemrxiv.8259011.v1 ◽

2019 ◽

Author(s):

Kaili Zhang ◽

Ryan Ash ◽

Gregory S Girolami ◽

Josh Vura-Weis

Keyword(s):

Transient Absorption ◽

Extreme Ultraviolet ◽

Xanes Spectrum ◽

Transient Absorption Spectroscopy ◽

Fast Time ◽

Edge Structure ◽

X Ray ◽

Ligand Charge Transfer ◽

X Ray Absorption ◽

Mlct State

Fe(II) coordination complexes are promising alternatives to Ru(II) and Ir(III) chromophores for photoredox chemistry and solar energy conversion, but rapid deactivation of the initial metal-to-ligand charge transfer (MLCT) state to low-lying (d,d) states limits their performance. Relaxation to a 5T2g state is postulated to occur via a metal-centered triplet state, but this mechanism remains controversial. We use femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy to measure the excited-state relaxation of Fe(phen)32+ and conclusively identify a 3T intermediate that forms in 170 fs and decays to a vibrationally hot 5T2g state in 40 fs. The shape of this M2,3-edge X-ray absorption near edge structure (XANES) spectrum is sensitive to the electronic structure of the metal center, and the high spin sensitivity, fast time resolution, and tabletop convenience of XUV transient absorption make it a powerful new tool for measuring the complex photophysics of transition metal complexes.

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Tracking the Metal-Centered Triplet in Photoinduced Spin Crossover of Fe(phen)32+ with Tabletop Femtosecond M-edge XANES

10.26434/chemrxiv.8259011.v2 ◽

2019 ◽

Author(s):

Kaili Zhang ◽

Ryan Ash ◽

Gregory S Girolami ◽

Josh Vura-Weis

Keyword(s):

Transient Absorption ◽

Extreme Ultraviolet ◽

Xanes Spectrum ◽

Transient Absorption Spectroscopy ◽

Fast Time ◽

Edge Structure ◽

X Ray ◽

Ligand Charge Transfer ◽

X Ray Absorption ◽

Mlct State

Fe(II) coordination complexes are promising alternatives to Ru(II) and Ir(III) chromophores for photoredox chemistry and solar energy conversion, but rapid deactivation of the initial metal-to-ligand charge transfer (MLCT) state to low-lying (d,d) states limits their performance. Relaxation to a 5T2g state is postulated to occur via a metal-centered triplet state, but this mechanism remains controversial. We use femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy to measure the excited-state relaxation of Fe(phen)32+ and conclusively identify a 3T intermediate that forms in 170 fs and decays to a vibrationally hot 5T2g state in 40 fs. A coherent vibrational wavepacket with a period of 250 fs and damping time of 0.66 ps is observed on the 5T2g surface, and the spectrum of this oscillation serves as a fingerprint for the Fe-N symmetric stretch. The results show that the shape of the M2,3-edge X-ray absorption near edge structure (XANES) spectrum is sensitive to the electronic structure of the metal center, and the high spin sensitivity, fast time resolution, and tabletop convenience of XUV transient absorption make it a powerful tool for studying the complex photophysics of transition metal complexes.

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Tracking the Metal-Centered Triplet in Photoinduced Spin Crossover of Fe(phen)32+ with Tabletop Femtosecond M-edge XANES

10.26434/chemrxiv.8259011 ◽

2019 ◽

Author(s):

Kaili Zhang ◽

Ryan Ash ◽

Gregory S Girolami ◽

Josh Vura-Weis

Keyword(s):

Transient Absorption ◽

Extreme Ultraviolet ◽

Xanes Spectrum ◽

Transient Absorption Spectroscopy ◽

Fast Time ◽

Edge Structure ◽

X Ray ◽

Ligand Charge Transfer ◽

X Ray Absorption ◽

Mlct State

Fe(II) coordination complexes are promising alternatives to Ru(II) and Ir(III) chromophores for photoredox chemistry and solar energy conversion, but rapid deactivation of the initial metal-to-ligand charge transfer (MLCT) state to low-lying (d,d) states limits their performance. Relaxation to a 5T2g state is postulated to occur via a metal-centered triplet state, but this mechanism remains controversial. We use femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy to measure the excited-state relaxation of Fe(phen)32+ and conclusively identify a 3T intermediate that forms in 170 fs and decays to a vibrationally hot 5T2g state in 40 fs. A coherent vibrational wavepacket with a period of 250 fs and damping time of 0.66 ps is observed on the 5T2g surface, and the spectrum of this oscillation serves as a fingerprint for the Fe-N symmetric stretch. The results show that the shape of the M2,3-edge X-ray absorption near edge structure (XANES) spectrum is sensitive to the electronic structure of the metal center, and the high spin sensitivity, fast time resolution, and tabletop convenience of XUV transient absorption make it a powerful tool for studying the complex photophysics of transition metal complexes.

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Attosecond x-ray transient absorption spectroscopy in graphene

Physical Review Research ◽

10.1103/physrevresearch.3.013144 ◽

2021 ◽

Vol 3 (1) ◽

Author(s):

Giovanni Cistaro ◽

Luis Plaja ◽

Fernando Martín ◽

Antonio Picón

Keyword(s):

Absorption Spectroscopy ◽

Transient Absorption ◽

Transient Absorption Spectroscopy ◽

X Ray

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X-ray transient absorption reveals the 1Au (nπ*) state of pyrazine in electronic relaxation

Nature Communications ◽

10.1038/s41467-021-25045-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Valeriu Scutelnic ◽

Shota Tsuru ◽

Mátyás Pápai ◽

Zheyue Yang ◽

Michael Epshtein ◽

...

Keyword(s):

Electronic Excitation ◽

Transient Absorption ◽

Transient Absorption Spectroscopy ◽

Electronic Relaxation ◽

Nonadiabatic Dynamics ◽

X Ray ◽

Organic Chromophores ◽

Dynamics Simulations ◽

X Ray Absorption ◽

Structure Calculations

AbstractElectronic relaxation in organic chromophores often proceeds via states not directly accessible by photoexcitation. We report on the photoinduced dynamics of pyrazine that involves such states, excited by a 267 nm laser and probed with X-ray transient absorption spectroscopy in a table-top setup. In addition to the previously characterized 1B2u (ππ*) (S2) and 1B3u (nπ*) (S1) states, the participation of the optically dark 1Au (nπ*) state is assigned by a combination of experimental X-ray core-to-valence spectroscopy, electronic structure calculations, nonadiabatic dynamics simulations, and X-ray spectral computations. Despite 1Au (nπ*) and 1B3u (nπ*) states having similar energies at relaxed geometry, their X-ray absorption spectra differ largely in transition energy and oscillator strength. The 1Au (nπ*) state is populated in 200 ± 50 femtoseconds after electronic excitation and plays a key role in the relaxation of pyrazine to the ground state.

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Transient absorption spectroscopy using high harmonic generation: a review of ultrafast X-ray dynamics in molecules and solids

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2017.0463 ◽

2019 ◽

Vol 377 (2145) ◽

pp. 20170463 ◽

Cited By ~ 28

Author(s):

Romain Geneaux ◽

Hugo J. B. Marroux ◽

Alexander Guggenmos ◽

Daniel M. Neumark ◽

Stephen R. Leone

Keyword(s):

Time Scales ◽

Harmonic Generation ◽

Absorption Spectroscopy ◽

Transient Absorption ◽

High Harmonic ◽

High Harmonic Generation ◽

Transient Absorption Spectroscopy ◽

Spectroscopic Techniques ◽

X Rays ◽

X Ray

Attosecond science opened the door to observing nuclear and electronic dynamics in real time and has begun to expand beyond its traditional grounds. Among several spectroscopic techniques, X-ray transient absorption spectroscopy has become key in understanding matter on ultrafast time scales. In this review, we illustrate the capabilities of this unique tool through a number of iconic experiments. We outline how coherent broadband X-ray radiation, emitted in high-harmonic generation, can be used to follow dynamics in increasingly complex systems. Experiments performed in both molecules and solids are discussed at length, on time scales ranging from attoseconds to picoseconds, and in perturbative or strong-field excitation regimes. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

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Photodissociation Structural Dynamics of TrirutheniumDodecacarbonyl Investigated by X-ray Transient Absorption Spectroscopy

The Journal of Physical Chemistry A ◽

10.1021/jp312663q ◽

2013 ◽

Vol 117 (39) ◽

pp. 9807-9813 ◽

Cited By ~ 9

Author(s):

Michael R. Harpham ◽

Andrew, B. Stickrath ◽

Xiaoyi, Zhang ◽

Jier Huang ◽

Michael W. Mara ◽

...

Keyword(s):

Absorption Spectroscopy ◽

Structural Dynamics ◽

Transient Absorption ◽

Transient Absorption Spectroscopy ◽

X Ray

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X-ray absorption spectroscopy and density functional analysis of the Fe3+ distribution profile on Al sites in a chrysoberyl crystal, BeAl2O4:Fe3+

Journal of Applied Crystallography ◽

10.1107/s160057671600042x ◽

2016 ◽

Vol 49 (2) ◽

pp. 385-388 ◽

Cited By ~ 1

Author(s):

Kanokwan Kanchiang ◽

Atipong Bootchanont ◽

Janyaporn Witthayarat ◽

Sittichain Pramchu ◽

Panjawan Thanasuthipitak ◽

...

Keyword(s):

Optical Properties ◽

Absorption Spectroscopy ◽

Density Functional ◽

Density Functional Theory Calculations ◽

Distribution Profile ◽

Laser Applications ◽

Edge Structure ◽

X Ray ◽

Site Distribution ◽

X Ray Absorption

Chrysoberyl is one of the most interesting minerals for laser applications, widely used for medical purposes, as it exhibits higher laser performance than other materials. Although its utilization has been vastly expanded, the location of transition metal impurities, especially the iron that is responsible for chrysoberyl's special optical properties, is not completely understood. The full understanding and control of these optical properties necessitates knowledge of the precise location of the transition metals inside the structure. Therefore, synchrotron X-ray absorption spectroscopy (XAS), a local structural probe sensitive to the different local geometries, was employed in this work to determine the site occupation of the Fe3+ cation in the chrysoberyl structure. An Fe K-edge X-ray absorption near-edge structure (XANES) simulation was performed in combination with density functional theory calculations of Fe3+ cations located at different locations in the chrysoberyl structure. The simulated spectra were then qualitatively compared with the measured XANES features. The comparison indicates that Fe3+ is substituted on the two different Al2+ octahedral sites with the proportion 60% on the inversion site and 40% on the reflection site. The accurate site distribution of Fe3+ obtained from this work provides useful information on the doping process for improving the efficiency of chrysoberyl as a solid-state laser material.

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