Browsing by Author "Peisach, Max"

Now showing 1 - 8 of 8
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    Analytical application of proton-induced prompt photon specrometry
    (1982) Gihwala, Dherendra; Peisach, Max
    Prompt gamma-rays emitted tinder bombardment with 3.5 to 6.0MeV protons from the 77 stable non-gaseous elements were evaluated for analytical application. The compilation included the yields of about 2200 gamma-rays and their detection limit for analysis. Because the data were measured under identical experimental conditions, the relative values may be generally applicable. For each element, the gamma-ray spectrum and the numerical data are presented in tables listing identified gamma-rays with yields and detection limits for Ep = 4.5 MeV, the gamma yields as a function of proton energy for the most intense gamma-prays, and, the polynomial coefficients of the function relating the detection limit to the bombarding energy. An Atlas of Spectra and a Catalogue of gamma-rays summarised the data.
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    Elemental analysis by alpha-induced prompt gamma-ray spectrometry
    (1978) Giles, Ian Stewart; Peisach, Max
    Alpha-induced prompt gamma-rays generated by excitation, or in nuclear reactions, were studied for 57 elements, to select those elements having gamma-rays of sufficient intensity for analytical application. Several light, medium and heavy elements show promise. Of these nitrogen, fluorine, manganese and vanadium were selected for more detailed study. The applicability of this technique was tested by studying the determination of fluorine in cements and of nitrogen, vanadium and manganese in steels.
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    Pixe analysis of adjacent elements
    (1991) Mateta, Nkaro Aldefrida; Peisach, Max; Pougnet, M A Bruno
    Proton induced X-ray emission (PIXE) analysis depends on the accurate stripping of the peaks of individual X-rays from the X-ray energy spectrum produced by the bombardment of a target material with charged particles. The energy separation between the Kᵦ X-ray of element Z and the Kα X-ray of element (Z + 1) increases with increasing Z. Accordingly, for adjacent lower Z elements, there is an overlap in energies between these two X-rays, and hence interference may be caused by one element in the determination of the other. The purpose of this investigation was to determine the extent of such possible interferences and to evaluate the accuracy and precision of the determination of adjacent elements, especially when one of the pair is present in overwhelming concentrations. Two elemental pairs, potassium-calcium, of biological significance, and vanadium-chromium, of metallurgical significance, were studied in detail. Mixtures of stock solutions of the two elements of each pair were made to provide samples with elemental ratios of the minor component decreasing from 10-¹ to 10-⁴ relative to the major one. A minimum of five of these samples were prepared on thin foils as well as on thick target pellets for each concentration level, and the PIXE spectra were recorded under bombardment with protons of 3 MeV. The spectra were analysed off-line by the program AXIL, which, in cases where the minor component could not be visually identified in the spectrum, was forced to evaluate the concentrations of both components. Under these conditions, low levels of the minor component were reported even though the component could not be resolved. All samples, the spectra of which showed the presence of both elements of the elemental pairs, could be analysed in mg/g concentration range. The precision and accuracy of such analysis were acceptable, except in the case of pellets onto which solutions containing both potassium and calcium were deposited. Chromatographic separation of potassium from calcium during the diffusion of the solution in the pellet matrix gave unacceptably erroneous results. When the concentration of the major component exceeded that of the minor by a factor of 200 or more, the presence of the minor component could no longer be recognised in the spectra. When such spectra were analysed by AXIL, forcing the program to determine both elements, results were a reflection of background levels in the energy region of the expected peak. It could therefore be concluded that the determination of the minor component in the presence of the major one for adjacent elements by PIXE is inaccurate for relative concentrations less than 1:200.
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    Some studies of the reaction between stannic chloride and silver perchlorate in anhydrous media
    (1954) Peisach, Max; Pugh, W; Sebba, F
    The theory of the chemical bond, particularly in compounds where the bonds are neither purely electrovalent nor purely covalent, has in recent years received a great deal of attention. Of the oxy-acids which can form ionic as well as covalent compounds, perchloric acid and sulphuric acid are of special interest because of the electronic symmetry and the stability of their anions, While compounds of the elements of group IV, in the divalent state, are known to be ionic, the exact nature of the bonds formed by these elements in the tetravalent state in their oxy-salts has as yet not been ascertained. It would, therefore, be of interest to review the perchlorates and sulphates of that group.
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    Thick target pixe analysis
    (1993) Pineda-Vargas, Carlos A; Peisach, Max; Thornton, David A
    The evaluation of the physical parameters governing the X-ray yield production in thick targets by charged particles was investigated and matrix correction factors (MCF) were calculated for a wide variety of materials including values for all pure non-gaseous elements or their compounds for the Kα and Lα X-ray lines. These factors were calculated for 1, 2, 3 and 4 MeV proton bombarding energies. A new methodology named 'common matrix type' (CMT) was developed for the determination of trace element concentrations in carbon-rich materials, such as most biological materials, with unknown matrix composition. A universal set of matrix correction factors (MCF) values for these materials was established for trace elements with Z ≥ 19 and irradiations with proton energies in the range of 1 to 4 MeV. A similar methodology was developed for silicon-rich and calcium-rich materials where the main components, Al, Si and Ca do not vary appreciably in their concentrations. CMT methodologies were applied successfully for the determination of trace elemental concentrations in a wide variety of thick target materials, which included archaeological cultural materials, biological tissues and geological ores. The technique of correspondence analysis was used for the statistical analysis of the extended data matrix generated in most of the applications. This technique of interpretation of multielemental data proved to be a valuable tool. Two modes of PIXE application, macro-mode and micro-mode, were evaluated at different ion bombarding energies ranging from 1 to 85 MeV. Experimental X-ray production cross sections at 66 and 85 MeV were evaluated and found to correlate well with theory based on the plane wave Born approximation (PWBA) for the Kα and Kβ lines. It was found that the irradiation of intermediate thickness samples of geological ores by energetic protons (66 MeV) is a suitable technique for the determination of small traces of rare earth metals with detection limits for analysis expected to be below the μg.g-1 range. The fact that energetic protons can be used means that no need for matrix correction is necessary. Micro-PIXE with low energy protons was found suitable for the determination of small traces of metals in human kidney stones and for the study of interrelationships between trace element concentrations with time of stone formation, in stones excreted from a single patient.
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    Vervlugtiging van metale tydens die droging van biologiese materiaal
    (1976) Fourie, Hermanus Ockert; Peisach, Max; Orren, M J
    Daar bestaan verskeie analitiese tegnieke vir die kwantitatiewe bepaling van spoorelemente in biologiese materiaal. Om elke tegniek aan die gevraagde vereistes van sensitiwiteit, reproduseerbaarheid en akkuraatheid te laat voldoen, word gebruik gemaak van gespesialiseerde instrumentasie. Met biologiese matryse verg die meeste van hierdie metodes egter 'n voorbereidende ontbindingsprosedure om die organiese materiaal af te breek. Dit impliseer droging gevolg deur droe of nat verassingsprosedures van die materiaal. Die vraag ontstaan egter of geakkumuleerde metale, deur organismes gemetaboliseer word tot vlugtige organiese verbindings, en indien wel, of dit die huidige, algemene analitiese metodiek wat gebruik word, enigsiens kan beinvloed. Aan die hand van mariene organismes, word in hierdie studie die radionukliedes van die elemente kroom, mangaan, yster, kobalt, sink, arseen, selenium, kadmium, antimoon en lood gebruik om 'n bydrae te lewet tot die begrip van metaboliese prosesse, en terselfdertyd lig te werp op die betroubaarheid van die analitiese tegnieke wat toegepas word.