"Standardless" procedures for quantitative electron probe X-ray microanalysis attempt to eliminate the need for standardization through calculation of standard (pure element) intensities. Either "first principles" calculations, which account for all aspects of X-ray generation, propagation, and detection, or "fitted standards" calculations, which use mathematical fits to measured intensities from a limited set of pure standards, can form the basis for standardless analysis. The first principles standardless analysis procedure embedded in the National Institutes of Health/National Institute of Standards and Technology comprehensive X-ray calculation engine and database, Desktop Spectrum Analyzer, has been tested against spectra measured on NIST standard reference materials, research materials, and binary compounds. The resulting distribution of errors is broad, ranging from -90% to +150% relative. First principles standardless analysis can thus lead to unacceptably large errors.

A new global relationship has been developed for predicting electron-excited bremsstrahlung intensities over a wide range of accelerating voltages 10–40 keV, atomic numbers 4–92, and x-ray energies 1.5–20 keV. The new relationship was determined empirically from the mathematical modeling of extensive data and is designed for calculating bremsstrahlung intensities in analytical procedures, such as those requiring peak-to-background measurements, where the direct measurement of the bremsstrahlung intensities is impracticable. The distribution of errors between the data and the model is symmetrical, centered around zero error with 63% of the values falling between ±10% relative error.

LITERATURE CITEDMore detailed discussion of the -ray interferences is given in earlier work (78).3) As already mentioned above, the possibilities of nuclear interferences are few at 10 MeV. It may be seen in column 3, Table I, that the only interference is between Li and B, 7Be is produced by 7Li(p,n)7Be and by 10B(p,o:)7Be.No other interference was detected by direct -ray spectrometry of elements irradiated at 10 MeV. With chemical separations, it would probably be possible to observe some ( , ) reactions on the lighter elements. Anyhow, if one considers all the Q-values for the nuclear reactions and the relative positions of the stable and of the radioactive isotopes for the studied elements, one sees that for all of them it is possible to find a suitable and interference free (p,n) reaction (except for Li and B). CONCLUSIONS 10-MeV proton activation may be used for the determination of trace concentrations of the 22 elements studied in this work; 47 radioisotopes and over 100 associated -rays are obtained via (p,n) reactions, thus offering a great choice to perform the analysis and a great selectivity (except for Li and B).This study was complemented by an application to the analysis of trace elements in 19 different matrices. In the case of these 19 matrices, 10-MeV proton activation is a powerfull technique because it is sensitive, selective, and also nondestructive.

Line shapes of atomic lines and soft x-ray emission bands measured with a wavelength dispersive spectrometer (WDS) with the Electron Probe Micro Analyzer (EPMA) are reviewed. Least square fitting to pseudo-Voigt profiles of the digitally measured spectra are used to account for the presence of non-diagram features (high and low energy satellites) and instrumental induced distortions. The effect of line width and relative intensities on the quality of fits is illustrated. Spectral distortions resulting from the presence of absorption edges within the analyzed wavelength region are illustrated for the case of FeLα,β emission bands for pure Fe and iron oxides. For quantitative analysis, an analytical approach is presented where the measured soft x-ray emission bands are corrected for self absorption before extracting the intensities from the experimental data.

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The specimen volume which i s sampled i n the analytical electron microscope (AEM) i s usually defined by a convolution o f the incident beam intensity profile and the spatial distribution which arises from elastic scattering of the beam electrons Myklebust 1979,1981).Such scattering causes beam electrons to deviate by an average angle of only a few degrees, thus relatively few elastic events result in deflections large enough to cause propagation normal t o the incident beam direction and parallel to the foil surfaces.However, another mechanism exists which can lead to energy deposition perpendicular t o the beam, namely the formation o f "Fast Secondary Electronstt (FSE),i .e those which have received kinetic energies up t o one half of the beam energy. The classical cross section,o , for this process i s (Evans 1955): 4 2 (do/dE) = (ne /E ) . ( ( 1 /~)~ + ( l / ( l -~) )~) where E i s beam energy, e i s the electronic charge and E = A E / E i s the normalized kinetic energy of the secondary electron. The inelastic scattering which generates the FSE causes only a small deflection of the incident beam, but the FSE leave the impact point a t an angle the original beam electron trajectory given by (Molter 1931): P to where t=E/511 (kev). For a primary electron energy of 100 keV and an FSE energy of A E = 2keV this angle P i s approximately 80 degrees. The FSE thus propagate nearly a t right angles t o the incident electron.Although the calculated yield of FSE i s relatively small, typically 1 t o 5% increasing w i t h atomic number, their energy i s such that their cross section for some ionization processes may be much greater than that o f the primary electron.The effect of the FSE i n degrading the spatial resolution o f electron lithography has previously been reported (Murata e t al 1981).We report here calculations of the effect of FSE on the spatial resolution of X-ray analysis in the AEM.We have incorporated FSE production into a Monte Carlo electron trajectory simulation developed for AEM use (Newbury and Myklebust 1981).Along each primary electron trajectory the probability of FSE production i s continuously evaluated.I f an FSE i s generated, the primary simulation i s interrupted and the FSE i s tracked until i t s energy drops below Ec, the lowest ionization energy of interest, o r i t escapes from the foil. Computation of the primary trajectory i s then resumed. Figure 1 compares, W 1

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Michael J.. Ed.; VCH: Weinhelm, I986 pp 566-568. (36) Righettr, Pler G.; Delpech, Marc; Molsand, Franpolse; Kruh, Jacques; Labie, Dominique €ktr@ofes/s 1883. 4 , 393-398. (37) Rlghettl, Pier G. In Rot& Structure. A Ractlcal Appraach; Creighton, T. E., Ed.; IRL Press: Oxford, 1989; pp 23-63. (38) Uveby, Britt M.; Pettersson, Per; Andrasko, Jan; Ineva-Fiygare, Lourdes; Johannesson, wrike; W g , Angeiika; Postel, Wilhelm; Domschelt, Albert Maul, Pler L.; Pletta, Pier 0.; Glenazza. Ellsabetta; (39) BlanchcBoslsk, Adrlana; Rlghettl, Pier 0.; Egen, Ned; Bier, Mllan €k-(40) Moehec. Richard, A.; Bier, Milan; Righettl, Pier G. €ktxpbofes/.s 1966, (41) Montiel, Maria D.; Carracedo, Angel; LopezRodrlguer, Isidro; Rodrlguez-Cahro, Maria S.; Cocheho, Luis; Huguet. Erniiio; Genb, Manuel €lectr;ophoresiS 1988, 8 , 288-272. Righetti, pler G. J . E k h e m . Blophys. A d e m 1986, 16, 141-164. trophoresis t988, 7. 128-133. 7, 59-66. (42) Stenman, Ulf H. In Rogress in Isoelectric ' Focusk?g and Isotachophoresis; Rlghettl, Pler G. Ed.; Elsevier: AmsterdamThe cdculath of quantltatlve electron microprobe compodtbnal mcrpr nqukes accurate correctkm for the background that arhsr from the X-ray brems&rahhm& Dmcwent 8trategk are apppflate for w a v w e X-ray epectn#rcopy (WDS) and energy4spemlve X-ray spectrometry (EDS). For WDS mapping, the dependence of the bremsstrahlung on averwe atomlc number can be used to make an indlrect calculatbn of the background appropriate to each locatlon In the map from the background measured on a known pure elemmi dandard. For EDS mapplng, the background can be meawred dkectty at each map location. For complex specimens, a comblned WDS-EDS measurement/background correctlon strategy can be applied.