ISSN:0049-8246    

DOI:10.1002/xrs.1300210202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

ISSN:0049-8246    

DOI:10.1002/xrs.1300210203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe enhancement of XRF intensity due to Rayleigh and Compton scattering in the target (which may occur after or before the photoelectric interaction) is commonly neglected in XRF spectrometry. However, this contribution can modify the XRF intensities to an appreciable extent, becoming a source of uncertainty for the computational methods of quantitative analysis. Analytical expressions are presented to describe the intensities of the corresponding four double interactions (which mix the photoelectric effect with the dominant types of scattering) that enhance the XRF intensity: Rayleigh‐photoelectric, Compton‐photoelectric, photoelectric‐Rayleigh and photoelectric‐Compton. These relationships are obtained by using an iterative solution of the Boltzmann transport equation for photons, suitable for the study of multiple scattering processes. It is shown that the first three chains contribute with discrete enhancements of the same energy of the XRF line. The last, in contrast, contributes with a short‐range continuous spectrum that overlaps the low‐energy tail of the peaks. This contribution can modify the line shape in a non‐symmetric way, making the unfolding of peaks from energy‐dispersive spectra more imprecise.The corrective terms to the XRF intensity are computed for both pure and composite materials. A common property to all of them is their azimuthal symmetry, a consequence of the isotropic behaviour of the photoelectric effect. As a rule, the chains with Rayleigh scattering predominate in the low‐energy regime and contribute between 1 and 10% of the primary XRF line. The chains with Compton scattering prevail at higher energy and their extent may exceed several tens percent. All the corrections show a broad range of variation depending on the incident energy, the composition of the target, which defines its attenuation properties for all the energies, and the incidence an

ISSN:0049-8246    

DOI:10.1002/xrs.1300210204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractImprovements to the fundamental parameter algorithm of x‐ray fluorescence analysis are considered. The algorithm involves the following effects: primary and secondary x‐ray absorption, secondary and tertiary fluorescence, excitation by scattered x‐rays, excitation by photoelectrons and excitation by the divergent primary beam. The algorithm allows one to calculate the spectral intensity of x‐ray tubes with both thick and electron transmission targets. A version of the algorithm that can be handled on a low‐capacity computer is proposed. The algorithm was tested experimentally on the analysis of rocks, but its algorithm may be applied to different substances and

ISSN:0049-8246    

DOI:10.1002/xrs.1300210205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractFirst‐ and higher order reflections from a molybdenum‐boron carbide multilayer (nominal 2d200 Å) have been studied. In the first order the apparent 2dspacing was found to increase, and then to decrease, with increasing wavelength and angle of incidence, whereas for higher orders it increased with order, converging to a limit (2d∞) of about 210.5 Å. Strong refraction effects were invoked to rationalize this behaviour, and the refraction constant δλwas found to vary from 2 × 10−3to 50 × 10−3for the wavelength range 23.5−135 Å. Experimental procedures to calibrate multilayers for soft x‐ray spectroscopy, by first determining 2d∞ and then δλvalues for various wa

ISSN:0049-8246    

DOI:10.1002/xrs.1300210206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA simple method for the determination of the composition of compounds and alloys by using the data for chemical shifts of x‐ray absorption edges is suggested. It is found that the calculated compositions of compounds are in good agreement with standard composition value

ISSN:0049-8246    

DOI:10.1002/xrs.1300210207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractComparison of the x‐ray analyser properties of trihydroxymethylaminomethane (TAM) and pentaerythritol (PET) crystals showed that the TAM crystal has a higher efficienc

ISSN:0049-8246    

DOI:10.1002/xrs.1300210208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA new laboratory x‐ray absorption fine structure (XAFS) spectrometer specially designed for measurements of the absorption spectra of light elements is presented. The spectrometer consists of a newly developed rotating‐anode x‐ray source of portable size, a power supply of low‐voltage and high‐current type, a vacuum x‐ray path, a Johann‐type curved monochromator, a cell unit for high‐temperature measurements, and a solid‐state detector (SSD) system with a single‐channel analyser. The SSD system can eliminate x‐rays of other orders to give x‐ray absorption data containing no noise due to high frequencies. A current control method is employed to suppress characteristic x‐rays emitted from filament and target materials. The performance of the spectrometer was evaluated by x‐ray absorption measurements on a copper foil at the Cu K‐edge at room temperature and on powdered gibbsite and aluminosilicates at the Al K‐edge. The results showed that the spectrometer is capable of obtaining good quality XAFS and x‐ray absorption near‐edge structure (XANES) spectra at Al and Cu K‐edges within about 2 h. Thus, both XAFS and XANES studies will be possible with the spectrometer for a wide range of elements from sodium to lanthanides by u

ISSN:0049-8246    

DOI:10.1002/xrs.1300210209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractAn energy‐dispersive x‐ray fluorescence method is described for the determination of iodine in seasoned photographic fixing solutions. The method employs a cesium internal standard and is intended to cover a concentration range ofca. 80–4000 μg g−1iodine. The precision [relative standard deviation (RSD)] of the iodine measurement was found to be 1.01% (1s) at the 2700 μg g−1level. The RSD of the fixer sample preparation was determined to be 0.79% (1s). The limit of detection for iodine was calculated to be 8.7

ISSN:0049-8246    

DOI:10.1002/xrs.1300210210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

ISSN:0049-8246    

DOI:10.1002/xrs.1300210212

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY