Recent developments in x-ray spectroscopy have shown that this technique is a very powerful tool for the analysis of small quantities of material. A distinction must be made here between microanalysis -the analysis for elemental composition of a small total amount of material - and trace analysis - the analysis of bulk material for the presence of certain elements at very low concentrations. By the use of chemical separation, a problem in trace analysis can be converted into a microanalytical situation. A major improvement in trace analysis has been achieved by the use of ion-exchange resin loaded onto filter paper to collect the element(s) of interest from a solution of the original sample. The analysis of these concentrates or of particulate matter filtered out of polluted air or water can be optimized because the total mass of the sample is small and the background due to scattered prirmary radiation can be minimized.

Much interest has become manifest recently in the use of solid-state detectors for energy dispersion x-ray analysis of samples of this type. The value of energy dispersion can be demonstrated by improved detection limits for samples containing only a few widely separated elements. However, resolution of state-of-the-art solid-state detectors is not adequate to separate the Kβ of one element from the Kα of the next higher atomic number among the transition metals. Thus the presence of a large number of immediate neighbor elements at widely different concentrations as in pollution samples suggests the need for crystal spectrometers.

The field of neutron activation analysis (NAA) has expanded significantly in the past decade, with the number of publications increasing from approximately 100 to more than 1000 per year. This phenomenon correlates with the greater availability of useful neutron sources, improvements in gamma-ray spectrometry equipment, and a rapid increase in successful NAA applications. A significant number of applications have been in the biomedical and environmental fields, especially in cases where elements must be measured at ultra-trace levels.

Electron optics techniques have been applied to the examination of various evidence materials common to forensic science. Vehicular paint fragments, a common evidence material, possess topographical features suitable for SEM analysis and composition variations in the form of chemically distinct layers and surface contaminant particles which can be characterized using energy dispersive X-ray analysis. The ability to analyze paint samples in terms of both topography and composition presents the potential of an extremely valuable tool for forensic investigators.

Over thirty automotive paint samples from many sources were examined in this study, using either the secondary electron image of the SEM or the SEM image combined with concurrent X-ray analysis by an energy dispersive System. Topographical pictures and X-ray spectra were recorded and comparisons between samples were made. Additional characterization of specimens was attempted through the analysis of individual paint layers.

The data obtained was used to group the paint samples into categories used for identification of the sample source. This information is valuable to several types of criminal investigation.

The results presented here have been obtained with a regular Philips universal spectrometer, equipped with an irradiation tube radically different from those normally used. Since we have previously described this tube in past papers (1) (2) (3), we will therefore only briefly recall its principle.

When starting this research program, our aim was to make possible the analysis of very light elements from sodium to boron, for a regular fluorescence spectrometer, without any modification of the spectrometer itself. As a matter of fact, the tube that we developed enabled us to reach this goal, but, moreover it opened some other possibilities :

• 1) heavier elements could also be analysed

• 2) thanks to the very low electric power required by this tube, a portable spectrometer could be built for field use

• 3) since it allowed a very convenient study of low energy X-rays, we could easily measure energy levels of external electrons and thus study the influence of chemical or crystallographical structure on the X-ray spectrum.

A flow proportional counter for ultrasoft x-ray applications has been constructed and used to measure proportional counter parameters in the ultrasoft x-ray region at atmospheric and subatmospheric pressures for counting gases of P-10 and methane. We find that at atmospheric pressures the parametrization given by Zastawny for describing gas amplification in proportional counters applies and have measured values for the parameters for P-10 and methane. For subatmospheric pressures the Zastawny parameters are inadequate. A new parametrizatlon is required. In addition, the linearity of the detector for x-rays of energies of 15 KeV to 0.5 KeV was measured for pressures ranging from 750 Torr to 150 Torr and found to be excellent in all pressure regions.

The present investigation shows that soft x-ray spectroscopy is an effective tool for investigating the surface region of metals and alloys from 10 to 1000 Å. Results are presented where soft x-ray spectroscopy was employed to investigate oxidation of metals and alloys, alloy dissolution, and protective coatings. By using the LII/LIII ratio of iron and titanium, the surface oxide thicknesses of these metals could be obtained, For Fe-Cr alloys there is an increase in the amount of chromium relative to chromium oxide with decreasing chormium content. The oxide surface of steel with a 50 Å metal protective coating was reduced when the protective metal oxide had a heat of formation greater than that of iron oxide. In Cu-30Zn alloys, the first 15 min of dissolution showed an increased copper enrichment in the surface of Cu-30Zn.

The new x-ray analysis method using photoeleetron spectrometry demands knowledge of differential photoionization cross sections of the subshells of the converter atoms used as intermediary between the x-ray spectrum and the photoelectron spectrum. These differential cross sections were determined for the most appropriate converter, the neon atom, in the energy range from 50 to 3000 eV. The total photoionization cross section was partitioned into contributions that arise from single ionization in the various subshells and from multiple processes. We present in tabular and graphical form: a) 1s, 2s and 2p total subshell cross sections; b) 1s, 2s and 2p differential cross sections at 54.73°; and c) ls, 2s and 2p differential cross sections at 90°. Accuracy is considered to be better than 3%, 7% and 5% at all energies for 1s, 2s and 2p cross sections, respectively.

Photoelectron spectrometry is shown to be an excellent technique for the analysis of x rays in the ultrasoft and soft x-ray regions. X rays are converted into photoelectrons which are ejected from a suitable atomic level, and the photoelectrons are analyzed with an electron spectrometer. The method is energy dispersive, provides a resolution ranging from 0.1 eV at 20 eV to 1.1 eV at 3 keV, and gives well-defined intensity characteristics throughout the range. The energy range can be extended into the 10 keV decade. Properties of the new technique are discussed, compared with conventional techniques, and exemplified by a series of measurements which include determination of the emission spectra of M x rays of yttrium to rhodium, L x rays of zirconium, and the band structures of molybdenum and holmium.

A new ESCA (electron spectroscopy for chemical analysis) instrument has been developed to provide high sensitivity and efficient operation for laboratory analysis of composition and chemical bonding in very thin surface layers of solid samples. High sensitivity is achieved by means of the high-intensity, efficient X-ray source described by Davies and Herglotz at the 1968 Denver X-Ray Conference, in combination with the new electron energy analyzer described by Lee at the 1972 Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy. A sample chamber designed to provide for rapid introduction and replacement of samples has adequate facilities for various sample treatments and conditioning followed immediafely by ESCA analysis of the sample.

Examples of application are presented, demonstrating the sensitivity and resolution achievable with this instrument. Its usefulness in trace surface analysis is shown and some “chemical shifts” measured by the instrument are compared with those obtained by X-ray spectroscopy.

Protons from a 3 MV Van de Graaff have been used to produce characteristic x-rays from 21 elements spanning the periodic table. Absolute Kα and Lα x-ray production cross sections have been determined, allowing one to calculate sensitivities for any given sample, detector geometry, and proton beam parameters. Elemental detectability limits are discussed assuming various backings (e.g., mylar, kapton, etc.) and matrix materials. The large number of available small proton accelerators throughout the United States promises wide applicability of this technique to environmental and biomedical analysis.

Tissue's two major components: lipid and protein, are of a primary importance, related as they are to the normal life states. Assay of protein and lipid (fat and lean) in vivo is of certain criticality in human disease states, such as wasting, edema, obesity and other dyscrasias involving body mass and fat-lean balance. Since the elemental composition of lipid and protein molecules differ in a significant and regular fashion, their mass absorption coefficients differ when radiation in the x-ray and lower energy gamma ray region is used. Two monochromatic photons, one in the 20 to 30 keV region, another in the 60 to 100 keV region, can be shown to exhibit an absorption ratio in a two component system of fat and lean which provides for a determination of the component mass ratios. Photons from x-ray machines and isotopic x- and gamma ray sources have been proposed for this. The radionuclide offers qualities of stability, small size and weight, portability, zero power consumption and, generally, a certain economy. The electron capture decay of 109Cd provides a gamma ray at 88 kilovolts and a daughter (Ag) Kα doublet at 22 keV. This fortuitous energy combination is advantageous in this differential absorptiometry. The 109Cd source provides for a stable geometry and calls for the simultaneous measurement of both photons by non-dispersive x-ray spectroscopic techniques. Ten mCi of 109Cd was incorporated into a sealed source, filtered for the silver Kβ1 x-ray (at 24. 942 keV) with 0. 1 mm palladium and collimated with a grazing aperture arrangement. Fat-lean tissue simulating standard samples three cm to ten cm in length and of various component ratios were studied. Component weight percent was determined using a function of the transmitted radiation. Determinations on water (the lean simulator) and polyethylene (the fat Simulator) as well as other materials produced absorption ratios concurring favorably with the known make-up of the Simulators.

In vitro dual beam analysis of muscle tissue samples showed a high degree of correlation with the results of ether lipid extractions. Using lipid extraction values as the standard, the x-ray absorptiometric technique produced percentage lipid levels averaging within 0. 5% of the extractions.

In vivo measurements of fat content of the triceps muscle area were compared with skinfold thickness measurements of the same area. Coefficient of correlation was 0. 88.

A computerized systetn, consisting of a fluorescence x-ray source (Philips), an Si (Li) detector (Ortec), and a mini Computer (Xerox) is currentiy in operation at The University of Texas M. D. Anderson Hospital and Tumor Institute, Experimentel Pathology Section, for the analysis of trace elements in biological specimens. The elements of interest are Fe, Cu, and Zn for possible significance in the detection and study of cancer. The detection system is being used for comparatively routine analysis of these elements, which are present in blood serum in the ppM range. With appropriate sample preparation techniques, using 1 ml of serum, the limit of detectability for these elements is estimated to be 100 ppB (1 in 107). Further refinement is possible, and research in this direction continues.

The rapid, quantitative and qualitative analysis of particulates on air filter samples is becoming increasingly important as more air pollution sampling stations are set up throughout the countiy. Although atomic absorption provides a sensitive technique for the analysis of many elements, the disadvantages of complex sample preparation, sample destruction and the necessity to analyze one element at a time make this technique unsuitable for a large volume of samples. X-ray energy spectroscopy when combined with automated sample handling and the latest dedicated data reduction systems provides a technique which enables the analyst to process large numbers of samples and obtain precise quantitative and qualitative data rapidly. This paper will describe the preparation and analysis of typical air filter type samples, and the steps taken to identify the elements in the samples and obtain computerized reduction of the data in μg/cm2, ppm or percent.

The normal hexagonal structure of collagen is rearranged to tetragonal by treatraent of rat-tail tendon with two molar tetra-methylammonium chloride. The tetragonal parameters are a = 19.9 and c = 29.6A. Quite regular packing is indicated by the clarity of the X-ray diffractogram. The diffractogram clarity is greatly improved with respect to the collagen treated only with saline solution, and is considerably improved with respect to collagen oriented by cross-linking with aliphatic diols.

Currently, making use of the phenomenon of total external reflection of x-rays by matter, lenses are being designed and constructed for use in x-ray telescopes, x-ray microscopes and small angle x-ray scattering cameras. One of the lenses under consideration for a biomedical application is a right-circular cylinder of nominal wall thickness coated with gold. Since the particular biomedical application is not demanding with respect to resolution and image quality in comparison with an x-ray telescope or an x-ray microscope, the imaging properties of the simple right-circular cylinder are satisfactory and the device economical to produce. A detailed study of its properties was undertaken. One of the most stringent requirements on the internal grinding and polishing of such a lens is the roundness of the cylinder. An interferometric method using a laser source enabled the diameter to be determined to one part in 106. Several tests of optical quality vere performed at 6328A in the visible and 8.34A in the X-ray region. A centered stop prevented the direct beam from reaching the screen. A point source of highly coherent 6328A radiation was located on the axis of the cylinder. The divergent beam of light striking the inside walls of the cylinder gives rise to a non-localized Airy-type diffraction pattern. If the surface finish is rough the diffraction pattern will show a star-like pattern at its center. Lack of roundness is indicated by poorly shaped diffraction fringes of low quality. Other optical tests at 6328A in the near and far field regions as well as in the “focal' plane also yield information concerning the roundness and smoothness of the optical element. The previous optical tests when repeated with 8.34A x-rays should give essentially the same general diffraction and interference effects noted with the 6328A radiation. However, most effects are not observable because of the poor resolution of x-ray film, Image forming tests clearly show the presence of barrel and pincushion type distortion.

X-ray spectrometric analysis is examined as an analytical tool for elemental determinations of atmospheric aerosols. Contamination levels of the several filters used for collection purposes are examined and the results reported. A calibration technique is described for analysis of several elements in the microgram range based on collection of saturated vapors of aqueous salt solutions. The calibration curves together with an analysis of sensitivity and lower limits of detection are shown. The technique is employed to monitor continuously aerosol content in the atmosphere during passage of a cold front.

Compositional and lattice constant control of non-magnetic garnet substrates are required for suitable lattice matching with epitaxially deposited magnetic thin film. Suitable substrates for this purpose are the simple and mixed rare earth garnets. Lattice constants were obtained on Czochralski grown crystals by conventional x-ray diffraction powder techniques with a precision of ± .0005Å. An x-ray fluorescence method was developed to determine crystal composition with a precision of ± 0.5 percent. The precision with which a can be determined indirectly by x-ray fluorescence is ± 0.0082Å, which is comparable with that from direct measurement.

The principle of the method that we proposed two years ago (1) to correct the matrix effects in quantitative diffractometry is briefly recalled and recent improvements are described. Some examples taken in geological field illustrate its possibilities.

A new field of application has been explored : thanks to a combination of this method with background measurement, a semi-quantitative estimation of the amount of amorphous material is made possible in any sample.

This correction technique can be used with any regular diffractometer : for this purpose we simply need to add a second measuring channel, the characteristics of which are given.

Finally we describe briefly the complementary electronics which have been designed in order to fully automate the apparatus, from the insertion of the samples to the printing of the results.

Measurements of x-ray production as a function of depth in a sample (ϕ(ρz) curves) are fundamental to the determination of the quantitative equations for relating x-ray intensity to composition in electron probe microanalysis. These ϕ(ρz) curves have been measured for four different voltages and a number of different tracers in aluminum, copper, silver arid gold as matrix elements. From these ϕ(ρz) curves the absorption correction curves (f(x) curves) can be calculated. Such curves have been obtained and comparison is made with the absorption correction equations of Philibert. The effect of a tilted sample on the absorption correction is also discussed.