ISSN:0049-8246    

DOI:10.1002/xrs.1300220502

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

年代:1993

数据来源: WILEY

ISSN:0049-8246    

DOI:10.1002/xrs.1300220503

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

年代:1993

数据来源: WILEY

摘要:

AbstractVariations of the relative intensities of the Lα1, Lβ1and Lβ2,3,15lines of gold from an x‐ray tube with its operating voltage in the near‐threshold region of Au L subshells were studied. Large variations in the intensity ratios were observed for the lines originating from different subshells, which attain limiting values at high excitation overvoltages. These variations are primarily due to the variation with the electron beam energy of the realative numbers of initial ionizations created by the electron beam in different subshells. Attempts have been made to explain these variations by calculating the relative intensity values of these lines using various empirical expressions ava

ISSN:0049-8246    

DOI:10.1002/xrs.1300220504

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

年代:1993

数据来源: WILEY

摘要:

AbstractA close‐coupled side‐source geometrical configuration is proposed for obtaining a high detection sensitivity for rare earth elements (57 ⩽Z⩽ 69) by radioisotope‐excited energy‐dispersive x‐ray fluorescence spectrometry. In this configuration a disc source of241Am (100 mCi), a high‐purity germanium detector and thin samles of rare earth elements on a Mylar backing are employed in an optimized geometry to achieve detection limits in the range 20–50 ng for these elements in a cou

ISSN:0049-8246    

DOI:10.1002/xrs.1300220505

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

年代:1993

数据来源: WILEY

摘要:

AbstractA comparison among current methods in x‐ray spectrometry showed that it is possible to abandon the traditional concept of comparing unknown samples with standards if it is expected that unknown samples with a rough surface can be determined directly without sample preparation. The error caused by the uncertainties of the fundamental parameters can be reduced and the effect of the attenuation in the x‐ray path on the intensities of the characteristic fluorescent x‐rays can also be accounted for by the introduction of the instrumental factorsPikwhich are initially determined. In order to speed up the calculation, a new iterative equation is presented in the direct determination method. In addition, a new way to select the starting values in the iteration and a simplified way to iterate the calculation are presented. With these improvements, the convergence in iteration is faster than b

ISSN:0049-8246    

DOI:10.1002/xrs.1300220506

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe values of Lisub‐shell fluorescence yields (ωi) and Coster–Kronig transition probabilities (fij) were evaluated using radiative and non‐radiative transition rates based on the relativistic Dirac–Hartree–Slater (RDHS) model for all the elements in the atomic number range 25 ⩽Z⩽ 96. The values of the Coster–Kronig‐corrected fluorescence (vi) and average L shell fluorescence (ϖL) yields were also evaluated and least‐squares fitted to obtain the polynomials representing them as a func

ISSN:0049-8246    

DOI:10.1002/xrs.1300220507

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

年代:1993

数据来源: WILEY

摘要:

AbstractConcentrates extracted from a lateritic mineral deposit were analysed for their rare earth (RE) content by energy‐dispersive x‐ray fluorescence (XRF) spectrometry. The L emission lines of the lanthanides were excited with the 22.1 keV Ag K radiation from an annular Cd‐109 radioisotope source. The problem of the extensive overlap of the L lines were solved by the AXIL program for deconvolution of XRF spectra. Individual REs were quantified by preparing semi‐transparent pellets of the concentrate with starch which served as dilutant and binder. This allowed correction for sample absorption with the light matrix program of the QXAS analysis package based on the fundamental parameter method. The method allowed the simultaneous determination of 12 rare earths contained in the sample, with a reproducibility of 2.0–29% and accuracy in the range 1.5–24% relative error without the use of standard materials. Detection limits achieved were in the range of 340 ppm for the heavy REs and 4000 ppm for th

ISSN:0049-8246    

DOI:10.1002/xrs.1300220508

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

年代:1993

数据来源: WILEY

摘要:

AbstractA spectrometer based on the use of monochromatic W Kα1radiation for trace element studies of rare earth elements up toZ= 68 is described. Examples including both liquid and solid samples are included. Special attention is given to the contributions arising from Compton scattering and multiple scattering in the sample matrix. The results are compared with those obtained using a241Am γ‐sou

ISSN:0049-8246    

DOI:10.1002/xrs.1300220509

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

年代:1993

数据来源: WILEY

摘要:

AbstractBoth energy‐ and wavelength‐dispersive systems were used to obtain Mα/Lα intensity ratios for Ta, W, Pt, Au, Pb and Bi at various overvoltages. A table of these ratios corrected for matrix absorption and detector efficiency is presented, in addition to an interpolatory function of Mα/Lα generated ratios vs. overvoltage, for each element. In addition, three differentZAFcorrection models were used to predict both detected and generated ratios. Finally, experimental Mβ/Mα ratios measured at different overvoltages are presented for the six elements c

ISSN:0049-8246    

DOI:10.1002/xrs.1300220510

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

年代:1993

数据来源: WILEY

摘要:

AbstractIn characteristic x‐ray intensity calculations, the total L spectrum can be represented by separate spectra from L1, L2and L3subshell transitions. The expressions presented here take into account the ionization not only of the L1, L2and L3subshells but also of the K shell. The approximating polynomials for the calculation of the radiative transition probability and the Koster‐Kroning transition probability are derived. Examples are presented of intensity calculations in multi‐component systems using the TEREN pr

ISSN:0049-8246    

DOI:10.1002/xrs.1300220511

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

年代:1993

数据来源: WILEY