scholarly journals Ultrafast pump/probe diffraction and spectroscopy experiments with FEL radiation: setup development from the soft to the hard x-rays with the aim of studying chemical processes

2011 ◽  
Author(s):  
Ivan Rajkovic ◽  
Sebastian Grübel ◽  
Wilson Quevedo ◽  
Simone Techert
Keyword(s):  
Chemical Processes ◽  
X Rays ◽  
Pump Probe ◽  
Radiation Setup

Principles of Trace Structure Analysis in Electron Microscopy

1975 ◽  
Vol 30 (9) ◽  
pp. 1188-1199
Author(s):  
W. Hoppe
Keyword(s):  
Structure Analysis ◽  
Three Dimensional ◽  
Main Idea ◽  
Chemical Processes ◽  
X Rays ◽  
Time Axis ◽  
Physico Chemical ◽  
Structural Work ◽  
Radiation Induced ◽  
Stable Molecule

Structure analysis done with X-rays or with electrons, corresponds to an averaging of the specimen configuration over the exposure time. Such an analysis leads to the structure of the specimen only if the configuration does not change during exposure or if the change is negligible (stable molecule, crystal). Some time ago for instable configurations the method of "trace structure analysis" was proposed. The present paper explains the general principles of this method in detail. The static image of the structure will be divided into a dynamic succession of images along the time axis ("three-dimensional film"). But this division is not really characteristic for the method (it is in fact trivial). The main idea is to work with non-significant three-dimensional elementary structures and to use redundancies of the radiation induced physico-chemical processes for the combination of these elementary structures. Obviously these "redundancy laws" can only be unravelled in detail by trace structural work. It will be shown further that for special classes of these laws correlation analysis and pattern recognition procedures can be applied

scholarly journals Interstellar Chemistry: Radiation, Dust and Metals

2008 ◽  
Vol 4 (S255) ◽  
pp. 238-245
Author(s):  
Marco Spaans
Keyword(s):  
Milky Way ◽  
Large Fraction ◽  
Chemical Processes ◽  
Molecular Gas ◽  
X Rays ◽  
Feedback Effects ◽  
Interstellar Chemistry ◽  
X Ray ◽  
Metal Abundances ◽  
Dust Surface

AbstractAn overview is given of the chemical processes that occur in primordial systems under the influence of radiation, metal abundances and dust surface reactions. It is found that radiative feedback effects differ for UV and X-ray photons at any metallicity, with molecules surviving quite well under irradiation by X-rays. Starburst and AGN will therefore enjoy quite different cooling abilities for their dense molecular gas. The presence of a cool molecular phase is strongly dependent on metallicity. Strong irradiation by cosmic rays (>200× the Milky Way value) forces a large fraction of the CO gas into neutral carbon. Dust is important for H2 and HD formation, already at metallicities of 10−4 − 10−3 solar, for electron abundances below 10−3.

scholarly journals Analysis of a measurement scheme for ultrafast hole dynamics by few femtosecond resolution X-ray pump–probe Auger spectroscopy

2014 ◽  
Vol 171 ◽  
pp. 93-111 ◽  
Author(s):  
Bridgette Cooper ◽  
Přemysl Kolorenč ◽  
Leszek J. Frasinski ◽  
Vitali Averbukh ◽  
Jon P. Marangos
Keyword(s):  
Auger Spectroscopy ◽  
X Rays ◽  
Core Hole ◽  
Pump Probe ◽  
X Ray ◽  
Molecular Systems ◽  
The Core ◽  
Probe Delay ◽  
Valence Region ◽  
Hole Migration

Ultrafast hole dynamics created in molecular systems as a result of sudden ionisation is the focus of much attention in the field of attosecond science. Using the molecule glycine we show through ab initio simulations that the dynamics of a hole, arising from ionisation in the inner valence region, evolves with a timescale appropriate to be measured using X-ray pulses from the current generation of SASE free electron lasers. The examined pump–probe scheme uses X-rays with photon energy below the K edge of carbon (275–280 eV) that will ionise from the inner valence region. A second probe X-ray at the same energy can excite an electron from the core to fill the vacancy in the inner-valence region. The dynamics of the inner valence hole can be tracked by measuring the Auger electrons produced by the subsequent refilling of the core hole as a function of pump–probe delay. We consider the feasibility of the experiment and include numerical simulation to support this analysis. We discuss the potential for all X-ray pump-X-ray probe Auger spectroscopy measurements for tracking hole migration.

scholarly journals Pyrolysis and Combustion Kinetics of Disposable Surgical Face Mask Produced During Covid-19 Pandemic

2021 ◽  
Author(s):  
Arshad Adam Salema ◽  
Yasmin Mohd Zaifullizan ◽  
Wong Wai Hong
Keyword(s):  
Weight Loss ◽  
Face Mask ◽  
Chemical Processes ◽  
X Rays ◽  
Combustion Kinetics ◽  
Heating Rates ◽  
Safe Disposal ◽  
Model Free ◽  
The Face ◽  
Kinetics Of

Abstract In order to prevent the spread of Covid 19, most countries have made face masks compulsory. Millions of face mask are disposed of daily in the community. Therefore, the aim of the present paper is to study the thermo-chemical (pyrolysis and combustion) behavior of the face mask for its safe disposal. The kinetic parameter activation energy was calculated using both the model-based Coats–Redfern method and model-free methods (Flynn-Wall-Ozawa, Kissinger-Akihara-Sunose, and Starink) at four different heating rates (5, 10, 15, and 20 °C/min). Physical morphology with elemental analysis was performed using field-emission scanning electron microscopy and energy-dispersive X-rays. Results have shown that face masks decompose in the temperature range of 320–480 °C during pyrolysis with a maximum derivative weight loss of 2.5 %/°C. Combustion took place between 200 and 370 °C with a maximum derivative weight loss of 1.25 %/°C. The average activation energies calculated using model-free methods for pyrolysis and combustion were ~135 kJ/mol and ~65 kJ/mol, respectively. The leftover residue for both pyrolysis and combustion was in the range of 1.35 to 3.50 wt.%. In conclusion, thermo-chemical processes are a promising method for the safe disposal of face mask waste.

scholarly journals Effect of Additive of Polymetallic Ores’ Tailin gs on Properties of Composite Cements

2016 ◽  
Vol 18 (2) ◽  
pp. 153 ◽  
Author(s):  
A.Zh. Aymenov ◽  
N.B. Sarsenbayev ◽  
T.M. Khudyakova ◽  
B.K. Sarsenbayev ◽  
A.T. Batyrkhanov ◽  
...  
Keyword(s):  
High Strength ◽  
Chemical Processes ◽  
High Tech ◽  
X Rays ◽  
Protective Properties ◽  
X Ray ◽  
Physical Chemical ◽  
Technological Production ◽  
Composite Cements ◽  
Positive Effect

The article analyzes the use of polymetallic ores’ tailings as a basis for production of composite cements and concrete, having protective properties against gamma and X-rays radiation, as well as high strength and lifetime. The main practically significant result is: the development of scientific and technological production bases of new high-tech type of multicomponent hydraulic binders for concretes – composite cements; the identification of new hydration products in composite cements with addition of polymetallic ores’ tailings; the development of optimal compositions of composite cements for concretes. It is established that the composite cements, that developed by us on the basis of polymetallic ores’ tailings, meet modern requirements i.e. its improve the construction-technical properties of material, have positive effect to the environment situation and allow to reduce the production cost of the final product. Their technology is low metal-intensive and<br />power-consuming. Studies of physical-chemical processes of composite cements structure formation with addition of polymetallic ores’ tailings have been conducted using methods such as chemical, X-ray phase, differential-thermal and electronmicroscopic analysis methods.

scholarly journals X-rays only when you want them: optimized pump–probe experiments using pseudo-single-bunch operation

2015 ◽  
Vol 22 (3) ◽  
pp. 729-735 ◽  
Author(s):  
M. P. Hertlein ◽  
A. Scholl ◽  
A. A. Cordones ◽  
J. H. Lee ◽  
K. Engelhorn ◽  
...  
Keyword(s):  
Laser Excitation ◽  
Ccd Camera ◽  
Single Shot ◽  
X Rays ◽  
Time Resolved ◽  
Pump Probe ◽  
Charge Coupled Device ◽  
X Ray ◽  
X Ray Absorption ◽  
Sample Damage

Laser pump–X-ray probe experiments require control over the X-ray pulse pattern and timing. Here, the first use of pseudo-single-bunch mode at the Advanced Light Source in picosecond time-resolved X-ray absorption experiments on solutions and solids is reported. In this mode the X-ray repetition rate is fully adjustable from single shot to 500 kHz, allowing it to be matched to typical laser excitation pulse rates. Suppressing undesired X-ray pulses considerably reduces detector noise and improves signal to noise in time-resolved experiments. In addition, dose-induced sample damage is considerably reduced, easing experimental setup and allowing the investigation of less robust samples. Single-shot X-ray exposures of a streak camera detector using a conventional non-gated charge-coupled device (CCD) camera are also demonstrated.

scholarly journals Demonstration of a picosecond Bragg switch for hard X-rays in a synchrotron-based pump–probe experiment

2019 ◽  
Vol 26 (4) ◽  
pp. 1253-1259 ◽  
Author(s):  
Mathias Sander ◽  
Roman Bauer ◽  
Victoria Kabanova ◽  
Matteo Levantino ◽  
Michael Wulff ◽  
...  
Keyword(s):  
Epitaxial Films ◽  
High Repetition Rate ◽  
X Rays ◽  
Sound Waves ◽  
Optical Pump ◽  
Pump Probe ◽  
X Ray ◽  
Benchmark Experiment ◽  
Probe Experiment ◽  
Pump Probe Experiment

A benchmark experiment is reported that demonstrates the shortening of hard X-ray pulses in a synchrotron-based optical pump–X-ray probe measurement. The pulse-shortening device is a photoacoustic Bragg switch that reduces the temporal resolution of an incident X-ray pulse to approximately 7.5 ps. The Bragg switch is employed to monitor propagating sound waves in nanometer thin epitaxial films. From the experimental data, the pulse duration, diffraction efficiency and switching contrast of the device can be inferred. A detailed efficiency analysis shows that the switch can deliver up to 109 photons s−1 in high-repetition-rate synchrotron experiments.

scholarly journals Extraction of Fast Changes in the Structure of a Disordered Ensemble of Photoexcited Biomolecules

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
H.-C. Poon ◽  
M. Schmidt ◽  
D. K. Saldin
Keyword(s):  
Structural Changes ◽  
Ultrashort Pulses ◽  
Fast Time ◽  
X Rays ◽  
Multiple Diffraction ◽  
Time Resolved ◽  
Pump Probe ◽  
Pump And Probe ◽  
Time Variations ◽  
Diffraction Patterns

Using pump-probe experiments of varying time intervals between pump and probe, the method of time-resolved crystallography has given many insights into the fast time variations of crystallized molecules as a result of photoexcitation. We show here that quantities extractable from multiple diffraction patterns of dissolved molecules in random orientations, as measured using powerful ultrashort pulses of X-rays, also contain information about structural changes of a molecule on photoexcitation.

scholarly journals Tracking the Local Structure Change during the Photoabsorption Processes of Photocatalysts by the Ultrafast Pump-Probe XAFS Method

2020 ◽  
Vol 10 (21) ◽  
pp. 7818
Author(s):  
Yohei Uemura ◽  
Toshihiko Yokoyama ◽  
Tetsuo Katayama ◽  
Shunsuke Nozawa ◽  
Kiyotaka Asakura
Keyword(s):  
Structural Change ◽  
Free Electron ◽  
Structure Change ◽  
Ground State Structure ◽  
X Rays ◽  
Geometrical Structures ◽  
Band Theory ◽  
Pump Probe ◽  
X Ray ◽  
Wide Range

The birth of synchrotron radiation (SR) facilities and X-ray free electron lasers (XFELs) has led to the development of new characterization tools that use X-rays and opened frontiers in science and technology. Ultrafast X-ray absorption fine structure (XAFS) spectroscopy for photocatalysts is one such significant research technique. Although carrier behavior in photocatalysts has been discussed in terms of the band theory and their energy levels in reciprocal space (k-space) based on optical spectroscopic results, it has rarely been discussed where photocarriers are located in real-space (r-space) based on direct observation of the excited states. XAFS provides information on the local electronic and geometrical structures around an X-ray-absorbing atom and can address photocarrier dynamics in the r-space observed from the X-ray-absorbing atom. In this article, we discuss the time dependent structure change of tungsten trioxide (WO3) and bismuth vanadate (BiVO4) photocatalysts studied by the ultrafast pump-probe XAFS method in the femtosecond to nanosecond time scale with the Photon Factory Advanced Ring (PF-AR) and the SPring-8 Angstrom Compact free-electron LAser (SACLA). WO3 shows a femtosecond decay process of photoexcited electrons followed by a structural change to a metastable state with a hundred picosecond speed, which is relaxed to the ground-state structure with a nanosecond time constant. The Bi L3 edge of BiVO4 shows little contribution of the Bi 6s electron to the photoabsorption process; however, it is sensitive to the structural change induced by the photoexcited electron. Time-resolved XAFS measurements in a wide range time domain and with varied wavelengths of the excitation pump laser facilitate understanding of the overall details regarding the photocarrier dynamics that have a significant influence on the photocatalytic performance.

Sign in / Sign up

Export Citation Format

Share Document