Testing ZAF and related procedures

1992 ◽  
Vol 50 (2) ◽  
pp. 1638-1639
Author(s):  
Kurt F. J. Heinrich
Keyword(s):  
Absorption Coefficient ◽  
Cross Section ◽  
Internal Consistency ◽  
List Type ◽  
Type Number ◽  
Data Types ◽  
Experimental Conditions ◽  
X Ray ◽  
Continuous Radiation

Conventional ZAF procedures, Pouchou and Pichoir's PAP and XPP procedures (transcribed into a ZAF format), Scott and Love's procedure, and the f(ρz) procedures by Brown and by Packwood (all described in ref.) were tested by a modular program in Turbopascal which permits selecting separately the procedures for electron deceleration, backscattering (except the ϕ(ρz) procedures),absorption, fluorescence by characteristic and by continuous radiation. Parameters such as the absorption coefficient, the J factor, fluorescent yield and inner shell cross section can also be selected from the menu.The data used for the evaluation are from binary specimens. They were collected from publications by various authors, with addition of some unpublished data generated at NBS by R. Marinenko and H. Konuma. The following data types were excluded: 1.most data obtained with x-ray emergence angles below 30°.2.single values, not corroborated by measurements of other concentrations or under other experimental conditions.3.sets of measurements showing lack of internal consistency.

Fluorescence effects in quantitative microprobe analysis

1990 ◽  
Vol 48 (2) ◽  
pp. 188-189
Author(s):  
S.J.B. Reed
Keyword(s):  
Microprobe Analysis ◽  
Depth Distribution ◽  
Exciting Radiation ◽  
Primary Radiation ◽  
List Type ◽  
Type Number ◽  
Computing Power ◽  
X Ray ◽  
Fluorescent Radiation

Characteristic fluorescenceThe theory of characteristic fluorescence corrections was first developed by Castaing. The same approach, with an improved expression for the relative primary x-ray intensities of the exciting and excited elements, was used by Reed, who also introduced some simplifications, which may be summarized as follows (with reference to K-K fluorescence, i.e. K radiation of element ‘B’ exciting K radiation of ‘A’):1.The exciting radiation is assumed to be monochromatic, consisting of the Kα line only (neglecting the Kβ line).2.Various parameters are lumped together in a single tabulated function J(A), which is assumed to be independent of B.3.For calculating the absorption of the emerging fluorescent radiation, the depth distribution of the primary radiation B is represented by a simple exponential.These approximations may no longer be justifiable given the much greater computing power now available. For example, the contribution of the Kβ line can easily be calculated separately.

Interactive multiple area spectrum integration (MASI)

1994 ◽  
Vol 52 ◽  
pp. 942-943
Author(s):  
John A. Hunt ◽  
Richard D. Leapman ◽  
David B. Williams
Keyword(s):  
Image Processing ◽  
Low Dose ◽  
Routine Analysis ◽  
Reference Image ◽  
Area Spectrum ◽  
List Type ◽  
Type Number ◽  
Image Processor ◽  
X Ray ◽  
Scanning Path

Interactive MASI involves controlling the raster of a STEM or SEM probe to areas predefined byan integration mask which is formed by image processing, drawing or selecting regions manually. EELS, x-ray, or other spectra are then acquired while the probe is scanning over the areas defined by the integration mask. The technique has several advantages: (1) Low-dose spectra can be acquired by averaging the dose over a great many similar features. (2) MASI can eliminate the risks of spatial under- or over-sampling of multiple, complicated, and irregularly shaped objects. (3) MASI is an extremely rapid and convenient way to record spectra for routine analysis. The technique is performed as follows:Acquire reference imageOptionally blank beam for beam-sensitive specimensUse image processor to select integration mask from reference imageCalculate scanning path for probeUnblank probe (if blanked)Correct for specimen drift since reference image acquisition

scholarly journals On the Properties of Wolf-Rayet Stars and Their Mass Loss

1982 ◽  
Vol 99 ◽  
pp. 203-207
Author(s):  
N. Panagia ◽  
M. Felli
Keyword(s):  
Mass Loss ◽  
Multiple Scattering ◽  
Radiation Temperature ◽  
List Type ◽  
Type Number ◽  
Lyman Continuum ◽  
Stellar Radiation ◽  
Total Luminosity ◽  
Continuous Radiation ◽  
Photospheric Radius

From consideration of the observed properties of the envelopes produced by mass loss in WR stars we find that: a)The velocity at the optical photosphere is in the range 200–800 km sb)The effective photospheric radius for the continuous radiation capable to ionize helium twice (γ < 228 A) is typically 5 to 15 times the optical photospheric radius.c)The radiation temperature in the Lyman continuum (γ < 912 Å) is around 5 × 104K. Therefore, most of the stellar radiation is emitted in the far UV and the total luminosity is considerably higher than currently estimated.d)Multiple scattering (N ≃ 20) of radiation in the interval 228–504 Å can provide most of the momentum needed to accelerate the wind up to the observed terminal velocities.

scholarly journals Solar X radiation

1965 ◽  
Vol 23 ◽  
pp. 45-52 ◽  
Author(s):  
C. de Jager
Keyword(s):  
Electromagnetic Radiation ◽  
Gamma Rays ◽  
Electronic Transitions ◽  
List Type ◽  
X Rays ◽  
Type Number ◽  
X Ray ◽  
Image Position ◽  
Electron Shells

X-ray bursts are defined as electromagnetic radiation originating from electronic transitions involving the lowest electron shells; gamma rays are of nuclear origin. Solar gamma rays have not yet been discovered.According to the origin we have : 1.Quasi thermal X-rays, emitted by (a) the quiet corona, (b) the activity centers without flares, and (c) the X-ray flares.2.Non-thermal X-ray bursts; these are always associated with flares.The following subdivision is suggested for flare-associated bursts :

scholarly journals A new catalogue of quasi-stellar objects

1986 ◽  
Vol 119 ◽  
pp. 51-52
Author(s):  
A. Hewitt ◽  
G. Burbidge
Keyword(s):  
Seyfert Galaxies ◽  
List Type ◽  
Type Number ◽  
Stellar Objects ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac ◽  
Similar Information ◽  
Quasi Stellar Objects ◽  
Objective Prism

We have prepared a new catalogue of QSOs and BL Lac objects containing approximately 3400 entries. A complete update of the Hewitt-Burbidge (1980) catalogue has been made with approximately another 2000 objects with known redshifts added. The references to discovery, magnitudes, redshifts, color, spectra and polarimetry have been updated for the objects listed in 1980, and complete new references are included for the new objects. In addition to the basic optical information, the new catalogue also contains X-ray, radio and infrared information for all objects. Absorption redshifts are listed when they are available. A supplementary catalogue which is now in preparation will contain similar information for objects described variously as Seyfert galaxies, N systems and AGNs. In doubtful cases we have used the operational dividing line ƶ = 0.1. All objects with ƶ < 0.1 are put in the supplementary catalogue unless their discoverers have unambiguously defined them as QSOs. With approximately twice as many objects included it is interesting to note that: a)There are still very few genuine BL Lac objects, ∼100.b)The largest number of additions has come from identifications using the objective prism-grism techniques.

scholarly journals The K-Band Hubble Diagram for X-Ray Selected Brightest Cluster Galaxies

1998 ◽  
Vol 179 ◽  
pp. 339-341
Author(s):  
R.G. Mann ◽  
C.A. Collins
Keyword(s):  
Star Formation ◽  
List Type ◽  
Type Number ◽  
Hubble Diagram ◽  
Technical Problems ◽  
X Ray ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
The Absolute ◽  
Small Dispersion

The Hubble (magnitude-redshift) diagram for brightest cluster galaxies (BCGs) is a classic cosmological tool, widely studied because of the remarkably small dispersion (∼ 0.3 mag) in the absolute optical magnitudes of low redshift BCGs (Postman and Lauer 1995). Extending the BCG Hubble diagram to higher redshifts would greatly enhance its role as a cosmological probe, but this has been frustrated by several technical problems: – the conventional means of cluster selection in the optical become increasingly compromised by projection effects at z > 0.1– at higher redshifts the interpretation of optical magnitudes becomes increasingly complicated by the effects of possible star formation.

scholarly journals 4 Years of Radio to X-ray Observations of 3C 273

1989 ◽  
Vol 134 ◽  
pp. 112-113
Author(s):  
T.J.-L. Courvoisier ◽  
E. I. Robson ◽  
A. Blecha ◽  
P. Bouchet
Keyword(s):  
Near Infrared ◽  
Optical Emission ◽  
Light Curves ◽  
Physical Parameters ◽  
List Type ◽  
Type Number ◽  
Rapid Variability ◽  
X Ray ◽  
Model Independent ◽  
Ir Emission

The quasar 3C273 has been repeatedly observed at radio, mm, IR, optical, UV and X-ray frequencies since December 1983. A complex pattern of continuum variations has been discovered, which can be used to provide model independent physical parameters, and to constrain different models. The main features revealed by our set of observations are: (i)A flux decrease by 40% in the 2–10 kev flux in 20 days in early 1984 (Courvoisier et al. 1987).(ii)Differences between the X-ray light curves at 0.5 keV and 2–10 keV.(iii)A drop in the mm to mid-IR emission by factors 2–4 in early 1986, while the near infrared flux remained stable (Robson et al. 1986).(iv)A decrease in the ultraviolet intensity of ∼40% in about 6 months in 1987 (Ulrich, Courvoisier and Wamsteker 1988).(v)Rapid variability in the infrared and optical emission on timescales as short as one day in 1988 (Courvoisier et al. 1988 and Robson, Courvoisier and Bouchet this conference).

Hitachi Model XMA-5 Electron Probe Microanalyzer

1968 ◽  
Vol 26 ◽  
pp. 308-309
Author(s):  
Tomura ◽  
Okano ◽  
Hara
Keyword(s):  
Electron Probe ◽  
High Performance ◽  
List Type ◽  
X Rays ◽  
Type Number ◽  
Fluorescence Excitation ◽  
X Ray ◽  
Electron Probe Microanalyzer ◽  
Scientific Instrumentation ◽  
Made In

The recent advancement in scientific instrumentation has been phenomenal. This is particularity true in the electron probe microanalyzer field. This paper describes the improvements made in the Hitachi Model XMA-5 Electron Probe Microanalyzer to achieve high performance.1.X-ray spectroscopy1-1.It is now possible to analyze a wide variety of elements including ultra light elements in minute concentrations with the advent of an increasing number of dispersing elements and high detectability.1-2.A linear crystal drive and direct wavelength read-out (with respect to the crystal) is employed in the spectrometer to assure simultaneous analyses of up to three elements by using three of the six crystals provided. For correction of absorbed X-rays and fluorescence excitation and with due consideration of the angular distribution of the characteristic X-rays, an X-ray take off angle of 38° (electron probe is incident vertically on the specimen surface) was adopted.

Imaging Properties of the Soft X-Ray Photon

1985 ◽  
Vol 43 ◽  
pp. 592-593
Author(s):  
D. Sayre
Keyword(s):  
Cross Section ◽  
Reaction Cross Section ◽  
Strong Dependence ◽  
Coherent Scattering ◽  
Reaction Cross ◽  
List Type ◽  
X Ray ◽  
Basic Properties ◽  
Imaging Characteristics ◽  
Biological Structures

Introduction. The soft x-ray photon (0.1-lkeV, wavelength l-10nm) is now available for the first time in large numbers, thanks to several new radiation sources (see below). This particle offers important new opportunities in the imaging of unprocessed biological structures, including intact biological cells in the natural and even living state.Basic properties. We begin by examining the basic properties of the particle which give it its special imaging characteristics.1.The reaction cross-section level of its principal imaging reaction, photoelectric absorption (Fig. 1). This cross-section, at 105- 106 barns/atom, is excellently matched to the thickness of the biological cell. The other principal imaging reactions in use today (scattering of 100keV electrons in electron microscopy, and coherent scattering of 0.15nm photons in x-ray crystallography; see Fig. 1) are best suited to cellular sections or substructures, and to macroscopic ordered specimens (crystals), respectively.2.The strong dependence of its reaction cross-section on Z (Fig. 1). For example, the 2.4nm photon images biological structures in the presence of water, due to its low reactivity with hydrogen and oxygen. In general, good image contrast is obtained without specimen processing, even for biological materials.

A Study on the Occurrence of Gold in Unoxidized Carlin-Type Ores in China Using AEM, SEM-EDX and SXRF

1990 ◽  
Vol 48 (2) ◽  
pp. 414-415
Author(s):  
Liu Yongkang ◽  
Liu Shirong ◽  
Wan Guangquan ◽  
Zhou Lindi ◽  
Li Jilian ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Gold Mineralization ◽  
Analytical Electron Microscopy ◽  
List Type ◽  
Type Number ◽  
X Ray ◽  
Combined Use ◽  
Analytical Electron ◽  
Scanning Electron ◽  
Gold Bearing

The knowledge about the occurrence of gold is essential both to the explanation for the genesis of gold mineralization in its deposits and to the evaluation and exploration or even smelt process of its ores. It has been well known that the gold occurrence in the Carlin-type ores still remains a difficult question to be answered because of the tiny scale of its locality and its very low content.This paper reports the results of our analysis on some gold bearing minerals in the Carlin-type ores discovered during recent years in China with combined use of analytical electron microscopy (AEM), scanning electron microscopy-energy dispersive X ray spectrometry (SEM-EDX) and synchrotron X ray flourescence analysis (SXRF) techniques as following:(1) Some gold occurred as submicron size grains in the ores (see Photo 1-4 and Figure 1-3) with grain size generally less than 0.2 micron.(2) It has been found by AEM and SEM-EDX observation and SXRF analysis that gold occurred as micrograins embedded in the boundaries of clay or quartz minerals rather than, as said, entered the lattice or adhered as a covering film to the surface of clay minerals (see Figure 4).

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