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Abstract  

Enhanced yields from CHIX studies on non-conducting samples have demonstrated conclusively that such yields are exceptionally high when compared to PIXE at low incident particle energies. This was confirmed with low energy14N+,16O+ and20Ne+ ions whose X-ray production crosssections are negligibly small for PIXE yields. In particular, a combination of low incident energies and high X-ray yields could be useful for XSQR investigations and elemental studies with low energy accelerators. Furthermore, extended studies on pure metal targets revealed that the PIXE yield could be improved by insulating the targets thus making them suitable to produce the CHIX yield under identical experimental conditions. This paper discusses the complementary and competitive features of PIXE and CHIX.

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Abstract  

Sensitive methods of elemental analysis have been developed using charged-particle beams. These techniques are usually insensitive to the effects of outer-shell electrons and provide little or no information on chemical bonding. The past 50 years has seen wide applications of various accelerator-based methods in different areas of analysis. This paper reviews the development and major advances of a variety of ion-beam techniques and their impact in analytical studies.

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Abstract  

Elemental analysis of ancient artefacts is of considerable benefit to the field of Archaeology and of general interest to earth scientists. Several techniques are currently available for this purpose, and in this paper the capabilities of PIXE (Particle Induced X-ray Emission), XRF (X-ray Fluorescence) and ICP-MS (Inductively Coupled Plasma - Mass Spectrometry) were evaluated to establish which of these instrumental methods was best suited especially for routine on-line usage. The elements of interest discussed in this paper are useful in archaeological provenance studies.

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Abstract  

High resolution (K) X-ray spectrometry preceded by activation with fast neutrons, neutrons from an isotope-source, and charged particles, is a novel development in the field of activation analysis. This paper describes the capabilities of these techniques and evaluates their analytical potential for the specific determination of the rare earths and Platinum Group Elements (PGE's) in small samples. The investigation took the form of a feasibility study which relied heavily on the low energy sensitivity of the detector used. Detection of the delayed X-rays was achieved with a 100 mm2 Ge detector whose ability to produce optimum photopeak-to-noise ratios formed the basis exploited in this investigation. Analytical conditions are demonstrated over a range of concentrations for the elements of interest and the potential of the technique for application to the general routine analysis of the rare earths and PGE's are discussed.

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Abstract  

Earlier work on Charge Induced X-rays (CHIX) was extended to include the X-ray energy region between 0.70 to 4.0 keV. Protons of 700 keV, and1H 2 + ion beams of equivalent proton energies in the range 350–450 keV were used to produce enhanced yields of L and MX-rays from a suitable selection of highly compacted non-conducting samples. Enhancement factors are given and possible applications are mentioned.

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Abstract  

Kinetics and concentration profile associated with the regulated radiodegradation of bilirubin in an organic solvent were assessed. The pure unconjugated specimen was prepared in chloroform (40.0 µM). The depletion of bilirubin was almost linear with dose, and complete degradation was accomplished with doses in excess of 100 Gy. The method was also evaluated for the explicit production of the long-wavelength isomer of biliverdin, which was characterized spectrometrically by an absorbance band in the region 600–650 nm. Results including differences in air, N2 and O2 purged samples are presented to identify the atmospheric medium for optimum production of biliverdin. The process was regulated by controlling the dose. The general rate constant of the depletion process was estimated at a dose rate of 5.67·10−2Gy·s−1. The method is a convenient substitute for light illumination studies of bilirubin.

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Abstract  

Biliverdin is a useful component in various aspects of biochemistry and biosynthesis, but its synthetic preparation is often long-winded. Micro-production (and subsequent isolation) by solar photolysis and gamma radiolysis of bilirubin provides rapid in vitro generation. Both methods are competitive, and this article discusses their merits and limitations for application in biosynthetic research. The investigation assumed a comparative study to evaluate the relative potential of the photolytic and radiolytic phenomena in this respect. The calculated rate of incident energy in the case of solar photolysis was roughly30.4.10-2 W, and about 5.70.10-4 W during gamma-irradiation (from a 137Cs source). In both cases the bilirubin (40 µM) degradation was pronounced in the initial few minutes of exposure, producing respective depletion rates of approximately 6.8 µM/min and 2.4 µM/min. Overall, both applications showed declining bilirubin concentrations close to 90%, after about 30 minutes. However, the corresponding production of biliverdin was higher by about 50% in the photolytic application. To account for heat-up effects in the photolytic application, thermal effects were studied up to 65 °C, and it was found that, as a result of this, a reduction in bilirubin concentration of about 40% was encountered. The species of interest were monitored spectrophotometrically, and the composite results showed that regulated production of biliverdin is possible under certain conditions.

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Abstract  

Extended work, involving background effects, to confirm the charge-inducedX-ray (CHIX) phenomenon is reported. PIXE studies in pure metal targets surroundedby a special type of glass insulating material (Macor) produced higher backgrounds,in general, compared to corresponding observations made in the absence ofthe insulator. Experiments were conducted using low-energy protons of 700keV and beam currents ranging between 1–10 nA. Signal-to-noise ratiosand detection limits are compared and discussed in the light of the unusualhigh X-ray yields produced by the CHIX phenomenon.

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Abstract  

The feasibility is explored of classifying human hair specimens according to their trace metal composition as determined by PIXE. Protons of 3.5 MeV were used to analyse 150 samples by energy-dispersive spectrometry using a Si(Li) detector. The methods of the Minimal Spanning Tree and Non-Linear Mapping were used to establish correlation among the specimens. As a result of distinct groupings obtained by these methods it was inferred that these techniques could usefully be applied to environmental pollution studies.

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Abstract  

A recently discovered phenomenon of excessively high X-ray production is discussed. The high yield is attributed to the build-up of potential on non-conducting targets irradiated with accelerated ion beams, and the subsequent discharge. Ion-beams of1H+,1H2 +,2H+,2H2 +,3He+,3He2+,4He+,14N+,14N2+,16O+ and20Ne+ were used. A new mechanism of X-ray excitation is proposed. The increased X-ray fluxes produced by this process are suitable for analytical applications of high specificity. The mechanism of excitation associated with the process, factors affecting the high X-ray yields, applications and a general overview of the studies undertaken with the various ion beams are given.

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