Femtosecond Spectroscopy of Chemically Reactive Solids: a Methodology

1992 ◽  
Vol 296 ◽  
Author(s):  
Weining Wang ◽  
Marc M. Wefers ◽  
Keith A. Nelson
Keyword(s):  
Real Time ◽  
Large Amplitude ◽  
Structural Phase ◽  
Excitation Pulse ◽  
Experimental Methodology ◽  
Single Shot ◽  
Lattice Vibrations ◽  
Structural Phase Transitions ◽  
Time Resolved ◽  
Time Basis

AbstractAn experimental methodology for recording femtosecond time-resolved observations of irreversible change in solids is described. The central problem posed is that the trime-dependent evolution must be observed on a single-shot (i.e. real-time) basis since the sample may be permanently altered after each excitation event. Preliminary demonstrations of real-time femtosecond spectroscopic observations are presented. In addition, one-shot data acquisition techniques open up the possibility of excitation intensities that greatly exceed optical damage threshholds of most samples. Since only one excitation pulse is used, cumulative damage mechanisms may be circumvented. Even if the sample is damaged in a single shot, in some cases the events of interest may be observed before damage occurs. The use of timed sequences of high-intensity excitation pulses to drive large-amplitude, coherent lattice vibrations is discussed. If successful, such large-amplitude lattice vibrations could assist crystalline chemical reactions or structural phase transitions.

Femtosecond time-resolved spectroscopy of soft modes in structural phase transitions of perovskites

1994 ◽  
Vol 50 (13) ◽  
pp. 8996-9019 ◽  
Author(s):  
Thomas P. Dougherty ◽  
Gary P. Wiederrecht ◽  
Keith A. Nelson ◽  
Mark H. Garrett ◽  
Hans P. Jenssen ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Structural Phase ◽  
Structural Phase Transitions ◽  
Time Resolved ◽  
Time Resolved Spectroscopy ◽  
Soft Modes

PROBING PHOTOINDUCED STRUCTURAL PHASE TRANSITIONS BY FAST OR ULTRA-FAST TIME-RESOLVED X-RAY DIFFRACTION

2004 ◽  
pp. 309-342 ◽  
Author(s):  
Hervé Cailleau ◽  
Eric Collet ◽  
Marylise Buron-Le Cointe ◽  
Marie-Hélène Lemée-Cailleau ◽  
Shin-ya Koshihara
Keyword(s):  
Phase Transitions ◽  
Structural Phase ◽  
Fast Time ◽  
Structural Phase Transitions ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray

scholarly journals Real time study of grain enlargement in zirconium under room-temperature compression across the α to ω phase transition

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Dmitry Popov ◽  
Nenad Velisavljevic ◽  
Wenjun Liu ◽  
Rostislav Hrubiak ◽  
Changyong Park ◽  
...  
Keyword(s):  
Phase Transition ◽  
Real Time ◽  
Room Temperature ◽  
Structural Phase ◽  
Structural Phase Transformation ◽  
Activation Barriers ◽  
Time Resolved ◽  
Microscopy Technique ◽  
Nano Crystalline ◽  
Time Scanning

Abstract We report a synchrotron Laue diffraction study on the microstructure evolution in zirconium (Zr) as it undergoes a pressure-driven structural phase transformation, using a recently developed real time scanning x-ray microscopy technique. Time resolved characterizations of microstructure under high pressure show that Zr exhibits a grain enlargement across the α-Zr to ω-Zr structural phase transition at room-temperature, with nucleation and growth of ω-Zr crystals observed from initially a nano-crystalline aggregate of α-Zr. The observed grain enlargement is unusual since the enlargement processes typically require substantially high temperature to overcome the activation barriers for forming and moving of grain boundaries. Possible mechanisms for the grain enlargement are discussed.

Laser photolysis and spectroscopy: a new technique for the study of rapid reactions in the nanosecond time range

1968 ◽  
Vol 308 (1492) ◽  
pp. 95-110 ◽  
Keyword(s):  
Laser Pulse ◽  
Absorption Spectra ◽  
Excitation Pulse ◽  
Laser Photolysis ◽  
New Technique ◽  
Time Range ◽  
Single Shot ◽  
Excited Singlet ◽  
Absorption Bands ◽  
Time Resolved

We have developed a new, very rapid, spectroscopic recording technique with the aid of which photographic absorption spectra of transient intermediates with lifetimes in the nanosecond time range can be obtained. The technique is a hundred times faster than present flash spectrographic instrumentation and provides time-resolved absorption spectra over a wide spectral range in a single experiment. Frequency-doubling is used to obtain both a 347 nm laser pulse suitable for excitation and a 694 nm laser pulse from a single Q -switched ruby laser pulse. The 694 nm pulse is converted into a continuum for absorption spectroscopy by bringing it to a sharp focus in a suitable gas, so as to cause a laser-induced breakdown spark. The excitation pulse has a duration of 30 ns. The duration of the continuum pulse varies with the gas used. In 1 atm of oxygen it has a duration of 30 ns, is synchronized to within 10 ns with the excitation pulse and has an intensity adequate for single-shot flash spectroscopy. The laser-induced spark in 1 atm of xenon has a duration of several μs and provides an excellent background continuum, of essentially constant intensity, for kinetic spectroscopy over periods up to 1 μs, using an image-converter camera to provide time resolution. We have applied the laser photolysis technique to observing, for the first time, absorption spectra arising from the lowest excited singlet states of several aromatic hydrocarbons. The time-resolved spectra obtained show the decay of the new excited singlet absorption bands and the concomitant build-up of triplet-triplet absorption bands during the first microsecond following light absorption, thus depicting graphically the non-radiative process of intersystem crossing from the lowest excited singlet state to the triplet manifold. The new bands also serve to locate the energies of higher excited singlet levels which, in many cases, are inaccessible from the ground state. The new technique should find wide application to solid, liquid and gaseous systems and should contribute to the understanding of photochemical primary processes in the time range 10 -9 to 10 -6 s. Eventual extension of the technique to the 10 -12 s range appears possible by using mode-locked lasers.

scholarly journals Single-Shot Multicontrast X-ray Imaging for In Situ Visualization of Chemical Reaction Products

2021 ◽  
Vol 7 (11) ◽  
pp. 221
Author(s):  
Margarita Zakharova ◽  
Andrey Mikhaylov ◽  
Vitor Vlnieska ◽  
Danays Kunka
Keyword(s):  
Real Time ◽  
Chemical Reaction ◽  
Single Shot ◽  
Reaction Products ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Imaging ◽  
In Situ Visualization ◽  
Different Time Scales

We present the application of single-shot multicontrast X-ray imaging with an inverted Hartmann mask to the time-resolved in situ visualization of chemical reaction products. The real-time monitoring of an illustrative chemical reaction indicated the formation of the precipitate by the absorption, differential phase, and scattering contrast images obtained from a single projection. Through these contrast channels, the formation of the precipitate along the mixing line of the reagents, the border between the solid and the solution, and the presence of the scattering structures of 100–200 nm sizes were observed. The measurements were performed in a flexible and robust setup, which can be tailored to various imaging applications at different time scales.

scholarly journals Sparsity-Based Recovery of Three-Dimensional Photoacoustic Images from Compressed Single-Shot Optical Detection

2021 ◽  
Vol 7 (10) ◽  
pp. 201
Author(s):  
Dylan Green ◽  
Anne Gelb ◽  
Geoffrey P. Luke
Keyword(s):  
Real Time ◽  
Acoustic Waves ◽  
Simulated Data ◽  
Initial Pressure ◽  
Single Pulse ◽  
High Energy ◽  
Image Sensor ◽  
Single Shot ◽  
Binary Mask ◽  
Time Resolved

Photoacoustic (PA) imaging combines optical excitation with ultrasonic detection to achieve high-resolution imaging of biological samples. A high-energy pulsed laser is often used for imaging at multi-centimeter depths in tissue. These lasers typically have a low pulse repetition rate, so to acquire images in real-time, only one pulse of the laser can be used per image. This single pulse necessitates the use of many individual detectors and receive electronics to adequately record the resulting acoustic waves and form an image. Such requirements make many PA imaging systems both costly and complex. This investigation proposes and models a method of volumetric PA imaging using a state-of-the-art compressed sensing approach to achieve real-time acquisition of the initial pressure distribution (IPD) at a reduced level of cost and complexity. In particular, a single exposure of an optical image sensor is used to capture an entire Fabry–Pérot interferometric acoustic sensor. Time resolved encoding as achieved through spatial sweeping with a galvanometer. This optical system further makes use of a random binary mask to set a predetermined subset of pixels to zero, thus enabling recovery of the time-resolved signals. The Two-Step Iterative Shrinking and Thresholding algorithm is used to reconstruct the IPD, harnessing the sparsity naturally occurring in the IPD as well as the additional structure provided by the binary mask. We conduct experiments on simulated data and analyze the performance of our new approach.

scholarly journals Real-time Hall-effect detection of current-induced magnetization dynamics in ferrimagnets

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
G. Sala ◽  
V. Krizakova ◽  
E. Grimaldi ◽  
C.-H. Lambert ◽  
T. Devolder ◽  
...  
Keyword(s):  
Hall Effect ◽  
Real Time ◽  
Hall Resistance ◽  
Single Shot ◽  
Switching Speed ◽  
Time Resolved ◽  
Pump Probe ◽  
Topological Quantum ◽  
Transverse Resistance ◽  
Hall Effect Measurements

AbstractMeasurements of the transverse Hall resistance are widely used to investigate electron transport, magnetization phenomena, and topological quantum states. Owing to the difficulty of probing transient changes of the transverse resistance, the vast majority of Hall effect experiments are carried out in stationary conditions using either dc or ac. Here we present an approach to perform time-resolved measurements of the transient Hall resistance during current-pulse injection with sub-nanosecond temporal resolution. We apply this technique to investigate in real-time the magnetization reversal caused by spin-orbit torques in ferrimagnetic GdFeCo dots. Single-shot Hall effect measurements show that the current-induced switching of GdFeCo is widely distributed in time and characterized by significant activation delays, which limit the total switching speed despite the high domain-wall velocity typical of ferrimagnets. Our method applies to a broad range of current-induced phenomena and can be combined with non-electrical excitations to perform pump-probe Hall effect measurements.

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