scholarly journals Out-of-equilibrium dynamics of photoexcited spin-state concentration waves

2015 ◽  
Vol 177 ◽  
pp. 363-379 ◽  
Author(s):  
A. Marino ◽  
M. Buron-Le Cointe ◽  
M. Lorenc ◽  
L. Toupet ◽  
R. Henning ◽  
...  
Keyword(s):  
Spin State ◽  
Spin Crossover ◽  
Laser Excitation ◽  
Intermediate Phase ◽  
Concentration Wave ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Equilibrium Dynamics ◽  
State Concentration

The spin crossover compound [FeIIH2L2-Me][PF6]2 presents a two-step phase transition. In the intermediate phase, a spin state concentration wave (SSCW) appears resulting from a symmetry breaking (cell doubling) associated with a long-range order of alternating high and low spin molecular states. By combining time-resolved optical and X-ray diffraction measurements on a single crystal, we study how such a system responds to femtosecond laser excitation and we follow in real time the erasing and rewriting of the SSCW.

scholarly journals Spin State Behavior of A Spin-Crossover Iron(II) Complex with N,N′-Disubstituted 2,6-bis(pyrazol-3-yl)pyridine: A Combined Study by X-ray Diffraction and NMR Spectroscopy

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 793
Author(s):  
Elizaveta K. Melnikova ◽  
Dmitry Yu. Aleshin ◽  
Igor A. Nikovskiy ◽  
Gleb L. Denisov ◽  
Yulia V. Nelyubina
Keyword(s):  
Nmr Spectroscopy ◽  
Spin State ◽  
Metal Ion ◽  
Spin Crossover ◽  
Molecular Design ◽  
Chemical Shifts ◽  
Variable Temperature ◽  
High Spin State ◽  
X Ray Diffraction ◽  
X Ray

A series of three different solvatomorphs of a new iron(II) complex with N,N′-disubstituted 2,6-bis(pyrazol-3-yl)pyridine, including those with the same lattice solvent, has been identified by X-ray diffraction under the same crystallization conditions with the metal ion trapped in the different spin states. A thermally induced switching between them, however, occurs in a solution, as unambiguously confirmed by the Evans technique and an analysis of paramagnetic chemical shifts, both based on variable-temperature NMR spectroscopy. The observed stabilization of the high-spin state by an electron-donating substituent contributes to the controversial results for the iron(II) complexes of 2,6-bis(pyrazol-3-yl)pyridines, preventing ‘molecular’ design of their spin-crossover activity; the synthesized complex being only the fourth of the spin-crossover (SCO)-active kind with an N,N′-disubstituted ligand.

Extreme Phonon Softening in Laser-excited Bismuth – Towards an Inverse Peierls-transition

2009 ◽  
Vol 1230 ◽  
Author(s):  
Wei Lu ◽  
Matthieu Nicoul ◽  
Uladzimir Shymanovich ◽  
Alexander Tarsevitch ◽  
Martin Kammler ◽  
...  
Keyword(s):  
Laser Excitation ◽  
Equilibrium Structure ◽  
Oscillatory Behavior ◽  
Intense Laser ◽  
X Ray Diffraction ◽  
Phonon Softening ◽  
Time Resolved ◽  
X Ray ◽  
Laser Fluences ◽  
Peierls Distortion

AbstractLarge amplitude coherent optical phonons have been investigated in laser-excited Bismuth by means of femtosecond time-resolved X-ray diffraction. For absorbed laser fluences above 2 mJ/cm2, the experimental data reveal an extreme softening of the excited A1g-mode down to frequencies of about 1 THz, only 1/3 of the unperturbed A1g-frequency. At even stronger excitation the measured diffraction signals no longer exhibit an oscillatory behavior presenting strong indication that upon intense laser-excitation the Peierls-distortion, which defines the equilibrium structure of Bismuth, can be transiently reversed.

scholarly journals Measuring non-equilibrium dynamics in complex solids with ultrashort X-ray pulses

2019 ◽  
Vol 377 (2145) ◽  
pp. 20170478 ◽  
Author(s):  
Michele Buzzi ◽  
Michael Först ◽  
Andrea Cavalleri
Keyword(s):  
Electronic Structures ◽  
Research Trend ◽  
Strong Interactions ◽  
X Rays ◽  
X Ray Diffraction ◽  
Optical Pulses ◽  
Time Resolved ◽  
X Ray ◽  
Equilibrium Dynamics ◽  
External Perturbations

Strong interactions between electrons give rise to the complexity of quantum materials, which exhibit exotic functional properties and extreme susceptibility to external perturbations. A growing research trend involves the study of these materials away from equilibrium, especially in cases in which the stimulation with optical pulses can coherently enhance cooperative orders. Time-resolved X-ray probes are integral to this type of research, as they can be used to track atomic and electronic structures as they evolve on ultrafast timescales. Here, we review a series of recent experiments where femtosecond X-ray diffraction was used to measure dynamics of complex solids. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

Evolution of laser-induced strain in a Ge crystal for the [111] and [100] directions probed by time-resolved X-ray diffraction

2021 ◽  
Vol 54 (6) ◽  
Author(s):  
Ranjana Rathore ◽  
Himanshu Singhal ◽  
Ajmal Ansari ◽  
Juzer Ali Chakera
Keyword(s):  
Propagation Velocity ◽  
Laser Excitation ◽  
Laser Pulses ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
Carrier Diffusion ◽  
X Ray ◽  
Strained Crystal ◽  
Different Depths ◽  
Silicon Based

Ultra-short laser-pulse-induced strain propagation in a Ge crystal is studied in the [111] and [100] directions using time-resolved X-ray diffraction (TXRD). The strain propagation velocity is derived by analysis of the TXRD signal from the strained crystal planes. Numerical integration of the Takagi–Taupin equations is performed using open source code, which provides a very simple approach to estimate the strain propagation velocity. The present method will be particularly useful for relatively broad spectral bandwidths and weak X-ray sources, where temporal oscillations in the diffracted X-ray intensity at the relevant phonon frequencies would not be visible. The two Bragg reflections of the Ge sample, viz. 111 and 400, give information on the propagation of strain for two different depths, as the X-ray extinction depths are different for these two reflections. The strain induced by femtosecond laser excitation has a propagation velocity comparable to the longitudinal acoustic velocity. The strain propagation velocity increases with increasing laser excitation fluence. This fluence dependence of the strain propagation velocity can be attributed to crystal heating by ambipolar carrier diffusion. Ge is a promising candidate for silicon-based optoelectronics, and this study will enhance the understanding of heat transport by carrier diffusion in Ge induced by ultra-fast laser pulses, which will assist in the design of optoelectronic devices.

scholarly journals Spin Crossover Metal-Organic Frameworks with Inserted Photoactive Guests: On the Quest to Control the Spin State by Photoisomerization

2021 ◽  
Author(s):  
Barbora Brachnakova ◽  
Jan Moncol ◽  
Jan Pavlik ◽  
Ivan Salitros ◽  
Sébastien Bonhommeau ◽  
...  
Keyword(s):  
Spin State ◽  
Elemental Analysis ◽  
Spin Crossover ◽  
Metal Organic Frameworks ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Trans Stilbene ◽  
Metal Organic ◽  
Trans Azobenzene

Three Hofmann-like metal-organic frameworks {Fe(bpac)[Pt(CN)4]}·G (bpac=1,2-bis(4-pyridyl)acetylene) were synthesized with photoisomerizable guest molecules (G = trans-azobenzene, trans-stilbene or cis-stilbene) and were characterized by elemental analysis, thermogravimetry and powder X-ray diffraction. The...

scholarly journals Formation of local spin-state concentration waves during the relaxation from a photoinduced state in a spin-crossover polymer

2017 ◽  
Vol 73 (4) ◽  
pp. 660-668 ◽  
Author(s):  
Céline Mariette ◽  
Elzbieta Trzop ◽  
Serhane Zerdane ◽  
Pierre Fertey ◽  
Daopeng Zhang ◽  
...  
Keyword(s):  
Long Range ◽  
Spin State ◽  
Thermal Equilibrium ◽  
Short Range ◽  
Short Range Order ◽  
Spin Crossover ◽  
Thermal Relaxation ◽  
X Ray ◽  
X Ray Scattering ◽  
State Concentration

The complex relaxation from the photoinduced high-spin phase (PIHS) to the low-spin phase of the bimetallic two-dimensional coordination spin-crossover polymer [Fe[(Hg(SCN)3)2](4,4′-bipy)2]nis reported. During the thermal relaxation, commensurate and incommensurate spin-state concentration waves (SSCWs) form. However, contrary to the steps forming at thermal equilibrium, associated with long-range SSCW order, the SSCWs forming during the relaxation from the PIHS phase correspond to short-range order, revealed by diffuse X-ray scattering. This is interpreted as resulting from the competition between the two types of SSCW order and another structural symmetry breaking, due to ligand ordering, occurring at low temperature and precluding long-range SSCW order.

Structural dynamics of photoinduced molecular switching in the solid state

2010 ◽  
Vol 66 (2) ◽  
pp. 189-197 ◽  
Author(s):  
Hervé Cailleau ◽  
Maciej Lorenc ◽  
Laurent Guérin ◽  
Marina Servol ◽  
Eric Collet ◽  
...  
Keyword(s):  
Solid State ◽  
Structural Dynamics ◽  
Degrees Of Freedom ◽  
Spin Crossover ◽  
Structural Information ◽  
Fast Time ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
Molecular Switching ◽  
X Ray

Fast and ultra-fast time-resolved diffraction is a fantastic tool for directly observing the structural dynamics of a material rearrangement during the transformation induced by an ultra-short laser pulse. The paper illustrates this ability using the dynamics of photoinduced molecular switching in the solid state probed by 100 ps X-ray diffraction. This structural information is crucial for establishing the physical foundations of how to direct macroscopic photoswitching in materials. A key feature is that dynamics follow a complex pathway from molecular to material scales through a sequence of processes. Not only is the pathway indirect, the nature of the dynamical processes along the pathway depends on the timescale. This dictates which types of degrees of freedom are involved in the subsequent dynamics or kinetics and which are frozen or statistically averaged. We present a recent investigation of the structural dynamics in multifunctional spin-crossover materials, which are prototypes of molecular bistability in the solid state. The time-resolved X-ray diffraction results show that the dynamics span from subpicosecond molecular photoswitching followed by volume expansion (on a nanosecond timescale) and additional thermoswitching (on a microsecond timescale).

scholarly journals Direct observations of shock-induced melting in a porous solid using time-resolved x-ray diffraction

2020 ◽  
Vol 4 (6) ◽  
Author(s):  
A. Mandal ◽  
B. J. Jensen ◽  
M. C. Hudspeth ◽  
S. Root ◽  
R. S. Crum ◽  
...  
Keyword(s):  
Porous Solid ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Direct Observations

scholarly journals Bulk modulus of H2O across the ice VII–ice X transition measured by time-resolved x-ray diffraction in dynamic diamond anvil cell experiments

2021 ◽  
Vol 103 (6) ◽  
Author(s):  
A. S. J. Méndez ◽  
F. Trybel ◽  
R. J. Husband ◽  
G. Steinle-Neumann ◽  
H.-P. Liermann ◽  
...  
Keyword(s):  
Bulk Modulus ◽  
Diamond Anvil Cell ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Diamond Anvil
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