scholarly journals Investigating the interstellar dust through the Fe K-edge

2017 ◽  
Vol 609 ◽  
pp. A22 ◽  
Author(s):  
D. Rogantini ◽  
E. Costantini ◽  
S. T. Zeegers ◽  
C. P. de Vries ◽  
W. Bras ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Cross Sections ◽  
Interstellar Dust ◽  
Effective Area ◽  
European Synchrotron Radiation Facility ◽  
Galactic Centre ◽  
X Rays ◽  
X Ray ◽  
Wide Range ◽  
The Individual

Context. The chemical and physical properties of interstellar dust in the densest regions of the Galaxy are still not well understood. X-rays provide a powerful probe since they can penetrate gas and dust over a wide range of column densities (up to 1024 cm-2). The interaction (scattering and absorption) with the medium imprints spectral signatures that reflect the individual atoms which constitute the gas, molecule, or solid. Aims. In this work we investigate the ability of high resolution X-ray spectroscopy to probe the properties of cosmic grains containing iron. Although iron is heavily depleted into interstellar dust, the nature of the Fe-bearing grains is still largely uncertain. Methods. In our analysis we use iron K-edge synchrotron data of minerals likely present in the ISM dust taken at the European Synchrotron Radiation Facility. We explore the prospects of determining the chemical composition and the size of astrophysical dust in the Galactic centre and in molecular clouds with future X-ray missions. The energy resolution and the effective area of the present X-ray telescopes are not sufficient to detect and study the Fe K-edge, even for bright X-ray sources. Results. From the analysis of the extinction cross sections of our dust models implemented in the spectral fitting program SPEX, the Fe K-edge is promising for investigating both the chemistry and the size distribution of the interstellar dust. We find that the chemical composition regulates the X-ray absorption fine structures in the post edge region, whereas the scattering feature in the pre-edge is sensitive to the mean grain size. Finally, we note that the Fe K-edge is insensitive to other dust properties, such as the porosity and the geometry of the dust.

scholarly journals Magnesium and silicon in interstellar dust: X-ray overview

2020 ◽  
Vol 641 ◽  
pp. A149
Author(s):  
D. Rogantini ◽  
E. Costantini ◽  
S. T. Zeegers ◽  
M. Mehdipour ◽  
I. Psaradaki ◽  
...  
Keyword(s):  
Cross Sections ◽  
Interstellar Dust ◽  
Galactic Centre ◽  
X Rays ◽  
Dust Grains ◽  
Large Reservoir ◽  
X Ray ◽  
Synchrotron Facility ◽  
The Galaxy ◽  
X Ray Binaries

Context. The dense Galactic environment is a large reservoir of interstellar dust. Therefore, this region represents a perfect laboratory to study the properties of cosmic dust grains. X-rays are the most direct way to detect the interaction of light with dust present in these dense environments. Aims. The interaction between the radiation and the interstellar matter imprints specific absorption features on the X-ray spectrum. We study them with the aim of defining the chemical composition, the crystallinity, and structure of the dust grains that populate the inner regions of the Galaxy. Methods. We investigated the magnesium and the silicon K-edges detected in the Chandra /HETG spectra of eight bright X-ray binaries, distributed in the neighbourhood of the Galactic centre. We modelled the two spectral features using accurate extinction cross-sections of silicates, which we measured at the synchrotron facility Soleil, France. Results. Near the Galactic centre, magnesium and silicon show abundances similar to the solar ones and they are highly depleted from the gas phase (δMg > 0.90 and δSi > 0.96). We find that amorphous olivine with a composition of MgFeSiO4 is the most representative compound along all lines of sight according to our fits. The contribution of Mg-rich silicates and quartz is low (less than 10%). On average we observe a percentage of crystalline dust equal to 11%. For the extragalactic source LMC X-1, we find a preference for forsterite, a magnesium-rich olivine. Along this line of sight we also observe an under-abundance of silicon ASi∕ALMC = 0.5 ± 0.2.

scholarly journals Extreme-ultraviolet- and X-Ray-driven Photochemistry of Gaseous Exoplanets

2022 ◽  
Vol 3 (1) ◽  
pp. 1
Author(s):  
Daniele Locci ◽  
Antonino Petralia ◽  
Giuseppina Micela ◽  
Antonio Maggio ◽  
Angela Ciaravella ◽  
...  
Keyword(s):  
Cross Sections ◽  
Atmospheric Chemistry ◽  
Extreme Ultraviolet ◽  
X Rays ◽  
Stellar Spectrum ◽  
X Ray ◽  
Spectral Bands ◽  
Wide Range ◽  
Chemical Conditions ◽  
Ultraviolet Photons

Abstract The interaction of exoplanets with their host stars causes a vast diversity in bulk and atmospheric compositions and physical and chemical conditions. Stellar radiation, especially at the shorter wavelengths, drives the chemistry in the upper atmospheric layers of close orbiting gaseous giants, providing drastic departures from equilibrium. In this study, we aim at unfolding the effects caused by photons in different spectral bands on the atmospheric chemistry. This task is particularly difficult because the characteristics of chemical evolution emerge from many feedbacks on a wide range of timescales, and because of the existing correlations among different portions of the stellar spectrum. In describing the chemistry, we have placed particular emphasis on the molecular synthesis induced by X-rays. The weak X-ray photoabsorption cross sections of the atmospheric constituents boost the gas ionization to pressures inaccessible to vacuum and extreme-ultraviolet photons. Although X-rays interact preferentially with metals, they produce a secondary electron cascade able to ionize efficiently hydrogen- and helium-bearing species, giving rise to a distinctive chemistry.

OBSERVATION OF INTERFERENCE BETWEEN ATOMIC BREMSSTRAHLUNG AND NUCLEAR BREMSSTRAHLUNG

1999 ◽  
Vol 09 (01n02) ◽  
pp. 1-10 ◽  
Author(s):  
K. ISHII ◽  
T. SATOH ◽  
S. MATSUYAMA ◽  
H. YAMAZAKI ◽  
Y. TOKAI ◽  
...  
Keyword(s):  
Cross Sections ◽  
Energy Region ◽  
Production Cross ◽  
Angular Distributions ◽  
X Rays ◽  
Beam Direction ◽  
Aluminum Target ◽  
X Ray ◽  
Wide Range ◽  
Mev Protons

An aluminum target was bombarded with 1.5 MeV protons and continuous x-rays were measured at the angles of 45°, 90° and 135° with respect to the beam direction. By investigating the shape of the x-ray energy spectrum, it was recognized that, the continuous x-rays below 12 keV are atomic bremsstrahlung (AB) and those of above 12 keV are nuclear bremsstrahlung (NB), and AB and NB are mingled in the energy region of around 12 keV The x-ray energy dependence of angular distributions presented well a change from the process of AB to that of NB in the continuous x-ray spectrum. Interference between AB and NB were discussed on the basis of PWBA theory. Continuous x-ray production cross sections were calculated on the basis of PWBA BEA and a semi-classical theory and compared with the experimental results. The theoretical prediction reproduced well the experimental cross sections over the wide range of 6 orders in magnitude and of 2 keV – 35 keV in the energy except for the energy region mingled with AB and NB. The ratio of the theoretical cross sections to the experimental ones showed an interference effect between AB and NB in their mingled region.

Ar K X-ray production in slow, highly charged Ar q+(q = 8–18) + Ar collisions

2002 ◽  
Vol 80 (12) ◽  
pp. 1579-1589 ◽  
Author(s):  
H Tawara ◽  
P Richard
Keyword(s):  
Cross Sections ◽  
X Rays ◽  
Enhanced Fluorescence ◽  
Energy Correlation ◽  
X Ray ◽  
Ion Collisions ◽  
Wide Range ◽  
First Time ◽  
Rotational Coupling ◽  
Shell Vacancy

In the present work, mechanisms of Ar K X-ray production have been investigated under low-energy Arq+ + Ar collisions in a wide range of the ion-charge states. Ar K X-rays have been observed as a function of the collision energy over (0.75–3.75)q keV/u and of the charge state over q = 8–16 of projectile Arq+ ions. If the L-shell vacancies become available (q = 9), Ar K X-ray yields are found to be enhanced roughly three orders of magnitude, compared with Ar8+ ions with no L-shell vacancy; to show some threshold; and to tend to quickly saturate at higher collision energies. The present analysis, based on the energy correlation diagrams of the quasi-molecules, suggests that Ar K X-rays originate entirely from target Ar atoms through promotion via the rotational coupling between 2pσ –2pπ molecular orbitals. Furthermore, the observed cross sections are found to increase nonlinearly with the projectile Arq+ ion charge q (q = 9). This can be understood because of the combined effects of two contributions: (i) the increased number of the L-shell vacancies of projectile Arq+ ions and (ii) the enhanced fluorescence yields of target Ar atom. In addition, Ar K X-rays have been observed under 2.5q keV/u Ar17+ and Ar18+ + Ar collisions and found to originate from the decay of K-shell vacancies initially present in the projectile Ar ions through electron capture into their highly excited states, followed by cascade down to the ground states. For the first time, though very weak, the X-rays due to the two-electron–one-photon transition, namely, K αα lines, have also been observed in bare Ar18+ ion collisions. PACS Nos.: 34.70+e, 32.80Rm

scholarly journals Modelling the properties of interstellar dust using the Si K-edge

2019 ◽  
Vol 15 (S350) ◽  
pp. 259-263
Author(s):  
Sascha Zeegers ◽  
Elisa Costantini ◽  
Daniele Rogantini ◽  
Cor de Vries ◽  
Harald Mutschke ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Cross Sections ◽  
Interstellar Dust ◽  
X Rays ◽  
X Ray ◽  
Synchrotron Facility ◽  
The Galaxy ◽  
Main Components ◽  
Distribution Composition ◽  
X Ray Binaries

AbstractThe properties of interstellar dust (ID) can be studied in great detail by making use of X-ray spectroscopy techniques. The radiation of X-rays sources is scattered and absorbed by dust grains in the interstellar medium. The X-ray band is especially suitable to study silicates - one of the main components of ID -since it contains the absorption edges of Si, Mg, O and Fe. In the Galaxy, we can use absorption features in the spectra of X-ray binaries to study the size distribution, composition and crystalline structure of grains. In order to derive these properties, it is necessary to acquire a database of detailed extinction cross sections models, that reflects the composition of the dust in the interstellar medium. We present the extinction profiles of a set of newly acquired measurements of 14 dust analogues at the Soleil Synchrotron facility in Paris, where we focus on silicates and the Si-K edge in particular, which is modelled with unprecedented accuracy. These models are used to analyse ID in the dense environments of the Galaxy.

Current developments in cosmic X-ray astronomy

1969 ◽  
Vol 313 (1514) ◽  
pp. 367-380 ◽  
Keyword(s):  
Background Radiation ◽  
X Rays ◽  
Launch Vehicles ◽  
Experimental Performance ◽  
X Ray ◽  
Wide Range ◽  
Diffuse Background ◽  
Wide Energy ◽  
The Individual

The purpose of this paper is to review the current developments in the observation of 0.2 to 100 keV X-rays originating outside the solar system. Discussion will be limited to experiments which are presently being developed and are likely to be flown within the next three years or so. Throughout this period experimental limits will continue to be set primarily by the available launch vehicles. Small rockets, and for energies above 20 keV, steerable balloons will continue to be the principal means of observation of cosmic X-rays, though with increasing use being made throughout the period of attitude controlled rockets (see, for example, Hazell, Cope & Walker 1968). In 1970 or 1971, the first satellite payloads specifically designed for cosmic X-ray studies should be launched, bringing a notable advance in sensitivity and resolution of the observations. There have been several excellent review articles published recently describing the different techniques useful in X-ray studies (e.g. Giacconiet et al . 1968; Aitken 1968) and therefore it is the present intention to review the current situation from the viewpoint of the observational aims of cosmic X-ray astronomy. For illustration of the kind of data to be expected in the period under review, reference will be made to a wide range of specific payloads. Performance figures quoted have been estimated by the author where not provided by the individual experimenter and and attempt has been made to achieve overall consistency in the criteria for judging experimental performance. The current observational aims of X-ray astronomy may be summarized as follows: (1) The detection of new sources, obtaining approximate positions and intensities. (2) Determination of accurate source positions, to facilitate identification studies. (3) Measurement of the size of a source and, if extended, also its structure. (4) Measurement of the detailed spectrum over a wide energy band for both discrete sources and the diffuse background radiation. (5) Study of source variability. (6) Measurement of polarization of the X-radiation.

scholarly journals Physical and chemical imaging of adhesive interfaces with soft X-rays

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Hiroyuki Yamane ◽  
Masaki Oura ◽  
Osamu Takahashi ◽  
Tomoko Ishihara ◽  
Noriko Yamazaki ◽  
...  
Keyword(s):  
Molecular Level ◽  
Covalent Bond ◽  
Chemical Imaging ◽  
Diglycidyl Ether ◽  
X Rays ◽  
X Ray ◽  
Covalent Bond Formation ◽  
Chemical States ◽  
The Individual ◽  
Physical And Chemical

AbstractAdhesion is an interfacial phenomenon that is critical for assembling carbon structural composites for next-generation aircraft and automobiles. However, there is limited understanding of adhesion on the molecular level because of the difficulty in revealing the individual bonding factors. Here, using soft X-ray spectromicroscopy we show the physical and chemical states of an adhesive interface composed of a thermosetting polymer of 4,4’-diaminodiphenylsulfone-cured bisphenol A diglycidyl ether adhered to a thermoplastic polymer of plasma-treated polyetheretherketone. We observe multiscale phenomena in the adhesion mechanisms, including sub-mm complex interface structure, sub-μm distribution of the functional groups, and molecular-level covalent-bond formation. These results provide a benchmark for further research to examine how physical and chemical states correlate with adhesion, and demonstrate that soft X-ray imaging is a promising approach for visualizing the physical and chemical states at adhesive interfaces from the sub-mm level to the molecular level.

scholarly journals Non-invasive sensing for food reassurance

The Analyst ◽  
2016 ◽  
Vol 141 (5) ◽  
pp. 1587-1610 ◽  
Author(s):  
Zou Xiaobo ◽  
Huang Xiaowei ◽  
Malcolm Povey
Keyword(s):  
Chemical Composition ◽  
Physicochemical Properties ◽  
Food Quality ◽  
Physical Principle ◽  
Quality Traits ◽  
X Ray ◽  
Main Food ◽  
Non Invasive ◽  
Wide Range ◽  
Nutritional Characteristics

The main food quality traits of interest using non-invasive sensing techniques are sensory characteristics, chemical composition, physicochemical properties, health-protecting properties, nutritional characteristics and safety. A wide range of non-invasive sensing techniques, from optical, acoustical, electrical, to nuclear magnetic, X-ray, biosensor, microwave and terahertz, are organized according to physical principle.

scholarly journals The XXL Survey

2018 ◽  
Vol 620 ◽  
pp. A18 ◽  
Author(s):  
C. H. A. Logan ◽  
B. J. Maughan ◽  
M. N. Bremer ◽  
P. Giles ◽  
M. Birkinshaw ◽  
...  
Keyword(s):  
Angular Resolution ◽  
False Positive Rate ◽  
High Sensitivity ◽  
Point Sources ◽  
Selection Function ◽  
X Rays ◽  
Cluster Emission ◽  
X Ray ◽  
Wide Range ◽  
Function Modelling

Context. The XMM-XXL survey has used observations from the XMM-Newton observatory to detect clusters of galaxies over a wide range in mass and redshift. The moderate PSF (FWHM ~ 6″ on-axis) of XMM-Newton means that point sources within or projected onto a cluster may not be separated from the cluster emission, leading to enhanced luminosities and affecting the selection function of the cluster survey. Aims. We present the results of short Chandra observations of 21 galaxy clusters and cluster candidates at redshifts z > 1 detected in the XMM-XXL survey in X-rays or selected in the optical and infra-red. Methods. With the superior angular resolution of Chandra, we investigate whether there are any point sources within the cluster region that were not detected by the XMM-XXL analysis pipeline, and whether any point sources were misclassified as distant clusters. Results. Of the 14 X-ray selected clusters, 9 are free from significant point source contamination, either having no previously unresolved sources detected by Chandra or with less than about 10% of the reported XXL cluster flux being resolved into point sources. Of the other five sources, one is significantly contaminated by previously unresolved AGN, and four appear to be AGN misclassified as clusters. All but one of these cases are in the subset of less secure X-ray selected cluster detections and the false positive rate is consistent with that expected from the XXL selection function modelling. We also considered a further seven optically selected cluster candidates associated with faint XXL sources that were not classed as clusters. Of these, three were shown to be AGN by Chandra, one is a cluster whose XXL survey flux was highly contaminated by unresolved AGN, while three appear to be uncontaminated clusters. By decontaminating and vetting these distant clusters, we provide a pure sample of clusters at redshift z > 1 for deeper follow-up observations, and demonstrate the utility of using Chandra snapshots to test for AGN in surveys with high sensitivity but poor angular resolution.

A multi-length-scale USAXS/SAXS facility: 10–50 keV small-angle X-ray scattering instrument

2013 ◽  
Vol 46 (5) ◽  
pp. 1508-1512 ◽  
Author(s):  
Byron Freelon ◽  
Kamlesh Suthar ◽  
Jan Ilavsky
Keyword(s):  
Small Angle ◽  
Soft Matter ◽  
High Energy ◽  
X Rays ◽  
X Ray ◽  
X Ray Scattering ◽  
Wide Range ◽  
And Performance ◽  
New Facility ◽  
Ray Scattering

Coupling small-angle X-ray scattering (SAXS) and ultra-small-angle X-ray scattering (USAXS) provides a powerful system of techniques for determining the structural organization of nanostructured materials that exhibit a wide range of characteristic length scales. A new facility that combines high-energy (HE) SAXS and USAXS has been developed at the Advanced Photon Source (APS). The application of X-rays across a range of energies, from 10 to 50 keV, offers opportunities to probe structural behavior at the nano- and microscale. An X-ray setup that can characterize both soft matter or hard matter and high-Zsamples in the solid or solution forms is described. Recent upgrades to the Sector 15ID beamline allow an extension of the X-ray energy range and improved beam intensity. The function and performance of the dedicated USAXS/HE-SAXS ChemMatCARS-APS facility is described.

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