ISSN:0049-8246    

DOI:10.1002/xrs.1300220102

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

年代:1993

数据来源: WILEY

摘要:

AbstractSeveral workers have proposed different models for the ionization distribution function ϕ(ρz), involving features related to the interaction of electrons with matter, e.g. ionization cross‐section, stopping power, electron back‐scattering and mass absorption coefficients (MACs). A number of expressions have been developed for these parameters, on which the accuracy of the correction procedures depends. This paper presents a comparison among three of the more successful models for ϕ(ρz): Packwood and Brown's Gaussian model, the quadrilateral model proposed by Sewellet al.and Pouchou and Pichoir's model.In order to test these models, a set of 1547 measurements in binary samples of known composition has been complied. Several models for the ionization cross‐section have been tested, along with different expressions for the mean ionization potentialJ, in which the shell effect can be taken into account. In addition, two possibilities for both the MACs and the electron backscattering coefficient are available. In general, all the tested models showed similar performances. Finally, the advantages of the models related to basic principles over the mathematically optimized ones, in the shape of ϕ(ρz) or in the parameters, are

ISSN:0049-8246    

DOI:10.1002/xrs.1300220103

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

年代:1993

数据来源: WILEY

摘要:

AbstractA Monte Carlo method was used to simulate relationships between substrate XRF intensities and film thicknesses for nickel film– and tin film–substrate systems. Experimental measurements of these relationships were performed for a few film–substrate systems. Good agreement between simulated and experimental values was obt

ISSN:0049-8246    

DOI:10.1002/xrs.1300220104

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

年代:1993

数据来源: WILEY

摘要:

AbstractX‐ray mass attentuation coefficients for the elements aluminium, copper, molybdenum and tantalum, the materials nylon, PTFE and lucite and the compounds magnesium sulphate, calcium sulphate chromium(III) acetate, cobalt acetate and zinc sulphate were measured using 6.46 keV photons from a57Co source and adopting a novel method employing a proportional counter spectrometer. For the elements and materials the close agreement of the measured μ/ρ values with the theoretical values indicates the suitability of the proposed method for studying the validity of the mixture rule in the case of compounds. For magnesium sulphate, calcium sulphate, cobalt acetate and zinc sulphate the measured μ/ρ values agree within 1% with the theoretically estimated values, indicating the validity of the mixture rule. However, with chromium(III) acetate, where the chromium K‐edge is less than the incident photon energy by only about 471 eV, the measured μ/ρ value shows a deviation of about – 11%. This is attributed to the effects of EXAFS and to the effects of the chemical environment on the μ/ρ value, which result in an uncertainty in the value of μ/ρ to be used when applying t

ISSN:0049-8246    

DOI:10.1002/xrs.1300220105

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

年代:1993

数据来源: WILEY

摘要:

AbstractA secondary effect simplified mathematical expression (SESME) was developed to calculate, in a very simple way, the XRF enhancement effect by secondary excitation. This approximate methods makes possible the use of a simple algorithm in the case of a finite thickness sample also. The numerical approximations are quantitatively estimated for samples of infinite thickness and the physical meaning of the formal expression is discussed.

ISSN:0049-8246    

DOI:10.1002/xrs.1300220106

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

年代:1993

数据来源: WILEY

摘要:

AbstractParticle‐induced x‐ray emission (PIXE) and Rutherford backscattering spectromatery (RBS) were used to analyse desert rose geological samples. Samples from the rose core and from the rose peripherals were studied. All samples were found to contain C, N, O, Na, Mg, Si, S, Cl, K, Ca, Ti, Mn, Fe and Sr. Core samples were found to contain more silicon than peripheral samples. The extra silicon in the rose core may suggest a mechanism for the formation of the rose through crystal growth on a seed of sili

ISSN:0049-8246    

DOI:10.1002/xrs.1300220107

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

年代:1993

数据来源: WILEY

摘要:

AbstractSmall dust samples of massca.0.07 g are fused with a lithium fluoride–lithium tetraborate flux to yield a homogeneous micro bead. These beads are presented to a wavelength‐dispersive spectrometer and the composition of the sample derived from calibrations effected with international standards. Matrix corrections are calculated by an NBSGSC algori

ISSN:0049-8246    

DOI:10.1002/xrs.1300220108

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe accuracy of Fundamental Parameter‐based XRF quantification is investigated for both bulk and multilayer analysis. It is found that for bulk materials the relative accuracy is of the order of 1% and for multilayers a few percent. The method can be set up in such a way that it contains an inherent validity check. Further possibilities of the Fundamental Parameter method are discusse

ISSN:0049-8246    

DOI:10.1002/xrs.1300220109

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

年代:1993

数据来源: WILEY

摘要:

AbstractCollimated and windowless energy‐dispersive x‐ray microfluorescence (XRF) analysis was performed in a scanning electron microscope (SEM). The observation and the positioning of the specimen area to be analysed were made possible by using a specially designed collimation system utilizing holed targets or a side‐entry multi‐target rod. Trace element detection with a lateral resolution of about 300 μm was obtained. The combined use of a windowless energy‐dispersive spectrometer and a‐thin‐foil aluminium target improved the peak‐to‐background ratio especially for oxygen and sodium in a standard glass specimen. A brief discussion of the improvement of this SEM micro‐XRF te

ISSN:0049-8246    

DOI:10.1002/xrs.1300220110

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

年代:1993

数据来源: WILEY

摘要:

AbstractA high‐precision, non‐destructuve x‐ray fluorescence (XRF) method has been developed for the determination of both trace and major elements in obsidian archaeological artifacts. Other than brushing the artifact surface clean, no sample preparation is required. The method developed proves XRF to be an extremely valuable technique for the analysis of archaeological obsidian samples which cannot be destroyed or altered because of their importance for historical studies. The method is applicable to both thick and thin samples which have wide variations in size and shapes. The method has been used to establish the provenance of a number of obsidian artifacts. The results ascertained for groups of samples from three provenances are discussed in this paper. The concentrations of thirteen trace (Ti, Mn, Zn, Ga, As, Rb, Sr, Y, Zr, Nb, Ba, Pb and Th) and three major (K, Ca and Fe) elements were determined from one x‐ray spectrum which was acquired during a 1000 s counting interval. The concentrations of the six most precisely measured elements (Fe, Rb, Sr, Y, Zr and Ba) yielded precisions which averaged 2.3%. The mean concentrations determined for five of these elements (excluding Y) differed on average by only 2.0% from published values which were ascertained by neutron activation analysis and XRF. The average standard deviations realized for the other ten elements determined w

ISSN:0049-8246    

DOI:10.1002/xrs.1300220111

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

年代:1993

数据来源: WILEY