Heavy Element Analysis Research Articles

Linking TEM Analytical Spectroscopies for an Assumptionless Compositional Analysis

The classical implementation for putting quantitative figures on maps to reveal elemental compositions in transmission electron microscopy is by analytical methods like X-ray and energy-loss spectroscopy. Typically, the technique in use often depends on whether lighter or heavier elements are present and-more practically-which calibrations are available or sample-related properties are known. A framework linking electron energy-loss spectroscopy (EELS) and energy-dispersive X-ray (EDX) signals such that absolute volumetric concentrations can be derived without assumptions made a priori about the unknown sample, is largely missing. In order to combine both techniques and harness their respective potentials for a light and heavy element analysis, we have set up a powerful hardware configuration and implemented an experimental approach, which reduces the need for estimates on many parameters needed for quantitative work such as densities, absolute thicknesses, theoretical ionization cross-sections, etc. Calibrations on specimens with known geometry allow the measurement of inelastic mean free paths. As a consequence, mass-thicknesses obtained from the EDX ζ-factor approach can be broken up and quantities like concentrations and partial energy-differential ionization cross-sections become accessible. ζ-factors can then be used for conversion into EELS cross-sections that are hard to determine otherwise, or conversely, connecting EDXS and EELS in a quantitative manner quite effectively.

New X-ray microprobe system for trace heavy element analysis using ultraprecise X-ray mirror optics of long working distance

A new X-ray microprobe system for trace heavy element analysis using ultraprecise X-ray mirror optics of 300 mm long working distance has been developed at beamline 37XU of SPring-8. A focusing test has been performed in the X-ray energy range 20–37.7 keV. A focused beam size of 1.3 μm ( V)×1.5 μm ( H) has been achieved at an X-ray energy of 30 keV, and a total photon flux of the focused beam was about 2.7×10 10 photons/s. Micro-X-ray fluorescence (μ-XRF) analysis of eggplant roots has been carried out using the developed microprobe. It is clearly observed in the XRF images that cadmium is highly accumulated in the endodermis, exodermis and epidermis of roots. This study demonstrates the potential of scanning microscopy for heavy elements analysis in the high-energy X-ray region.

Unique capabilities of heavy ion elastic recoil detection with gas ionization detectors

Specific aspects of heavy ion elastic recoil detection (ERD) with gas ionization detectors have been studied using representative measurements. A particular strength of the technique is the detection and direct quantification of elements with atomic numbers in the range Z=2–8, which are often not accessible with other ion beam techniques. Within the wider spectrum of analytical techniques in materials science, heavy ion ERD has unique capabilities, when the particular problem requires in addition the analysis of heavy elements or hydrogen detection. Whenever only heavy element analysis or only hydrogen profiling is of interest, alternative techniques tend to be superior.

Trace Heavy Element Analysis Using X-Ray Fluorescence with Quasi Monochromatic High-Energy Photons: Iodine in an Environmental Sample

X-ray fluorescence with high-energy photon excitation is a promising method for heavy element analysis. For trace determination, however, it is necessary to optimize the excitation spectrum. In this study, quasi monochromatization by a primary-beam filter and by a secondary target is quantitatively studied in order to detect an important bioelement, iodine, in an environmental sample. The primary-beam-filter technique gives the lowest detection limit, which is 1/5th the limit given by white excitation.

Energy straggling induced errors in heavy-ion PIXE analysis

Numerical calculations of the heavy-ion energy straggling influence on quantitative heavy ion PIXE analysis are presented. Heavy ion electronic straggling was calculated using semi-empirical model of Yang. Since heavy ion nuclear straggling is significant and in some cases larger than the electronic one, it has also been included into the calculations. Energy variations of K ionization cross sections were calculated using the ECPSSR model. Results for heavy ions are compared with those for protons, for the case of heavy element analysis in a light matrix and for the case of light element analysis in a heavy matrix. Implications on the quantitative heavy ion PIXE analysis are discussed.

Light and heavy element profiling using heavy ion beams

The analysis of thin layers in a near surface region with high resolution is an important problem in ion beam analysis. Here elastic recoil detection analysis (ERDA) using high energetic heavy incident ions has been optimized for analysis of light elements such as H, D, He, but has also proven its applicability for medium light elements up to B and C. The use of high energetic heavy incident ions, 8–16 MeV 16O and 30 MeV 58Ni from a 3 MV tandem accelerator, increased the depth resolution for H analysis by a factor of 3 compared with standard ERD using 2 MeV 4He. Additionally, the sensitivity of the method was increased by up to one order of magnitude, when the heaviest ion was used. In this experiment primary ions, scattered in forward direction into the detector, were suppressed using an absorber foil. When heavy ions are used, not only H recoils can transmit through the absorber foil, but also light and medium heavy recoils. The energy loss in the foil can be accurately calculated using the well-known TRIM code. The depth resolution obtained in this experiment was 100 Å in metallic samples (Cu, Nb), where the stopping power is high and 250 Å in samples with lower Z as e.g. Si and B. For all recoil species the depth resolution was dominated by straggling in the absorber foil and kinematic broadening. Therefore, the depth resolution did not vary much for different recoils. Simultaneously with the ERDA investigations Rutherford backscattering spectrometry (RBS) with heavy ions has been employed for heavy element analysis. The good mass separation which can be obtained using heavy projectile ions was used to optimize the depth resolution by tilting the sample. A multilayer of 5 Si Nb layers of 50 Å thickness each were clearly separated at 67.5° incident angle.

Lanthanide negative ion detection using accelerator mass spectrometry

Accelerator mass spectrometric methods have been used in the detection of the negative ions of the lanthanides. All of the lanthanide negative ions (La −−Lu −) have been observed except Pm −, Ho −, and Er −. The heavy element analysis line at the IsoTrace Laboratory was used to count the positive ions resulting from the atomic negative ions produced in a Cs sputter ion source and passed through the tandem accelerator. Because of its very low electron affinity, Dy − had a terminal voltage dependent yield, and its study required the reduction of the electric field gradients used to accelerate the ions. The relative negative ion yields among the lanthanides will be discussed. Both Yb − and Lu − have recently been theoretically predicted to exist in negative parity ground states.

AMS advances in the geosciences and heavy-element analysis

Abstract Until recently small accelerators, such as the 2 MV Tandetron, have been used only for the lighter elements such as 10Be, 14C and 26Al, while the heavier isotopes such as 36Cl, 41Ca and 129I have been perceived to need the higher energies only available on large machines. We describe the use of a Tandetron for measurement of 129 I 127 I at natural levels, and the in situ assay of some heavy elements of interest in economic geology at detection levels superior to those of more widely used techniques. A few recently described novel applications of AMS are also given.

Heavy element analysis by low energy accelerator mass spectrometry

Improvements have been made to the mass and energy analysis system at the IsoTrace Laboratory that have resulted in a factor of 30 increase in detection efficiency for some heavy ions and have reduced interference from the fragmentation of hydrides and other molecules. The implications of these improvements for the detection of rare atomic negative ions and radioisotopes such as 129I will be discussed. Evidence is also presented for the existence of a barium negative ion that is completely resolved from barium mono-, di- and trihydride interferences and which is clearly distinguished from any interference due to the fragmentation of BaH − 2 to BaH − before the first analyzing magnet.

A comparison of conventional and specimen isolation filtering techniques for the SIMS analyses of geologic materials

Ion microprobe measurements of relative ion intensities and charging potentials of geologic specimens are reported using two forms of kinetic energy filtering, conventional energy filtering (CEF) and specimen isolation (SI) conditions which analyze ∼ 100 eV and ∼ 500 eV ions, respectively. Both techniques give similar M + and M 2+ intensities, but molecular ion intensities are greatly decreased in the SI mode. This increased molecular ion suppression is of greatest importance for heavy element analysis such as in complete rare earth analysis. In the SI mode, with a 3 mm cover plate aperture, samples charge to very similar potentials (530 V ± 10% below the SAV) regardless of the primary beam current or the target structures (e.g. glass, ceramic, or bulk crystal). For either the SI or CEF techniques, the different matrices generally give very similar ion intensities referenced to 28Si +, showing that structural matrix effects can be neglected with either kinetic energy filtering technique. Glass standards can thus be readily used for quantitative analyses of minerals.

Hydrogen analysis as a function of depth for hydrogenous films and polymers by proton recoil detection

A quantitative analysis of the hydrogen content of a material, as a function of depth, may be achieved by energy analysis of protons recoiled from a sample of the material subject to MeV helium ion bombardment. The work presented includes an experimental determination of the cross-section for recoil production which is compared to theoretical predictions. Data is presented from the analysis of hydrogenous films and polymers. For the latter, the analysis has been performed on MeV heavy ion implanted material as well as pristine samples. The particular advantages of this technique are that it is compatible with and complementary to Rutherford backscattering (RBS) analysis for heavy element analysis, and it is less destructive and has a higher cross section than other nuclear reaction techniques.

Evaluation of the New Generation of Dual-Anode X-ray Tubes

Traditionally users of x-ray spectrometers have been forced to optimize their instrument for light element analysis and heavy element analysis through the choice of either a light or heavy element anode. The advent of the rhodium tube brought some relief to this situation, but some compromise was still required. The recent addition of the scandium side-window tube to the range has provided twice the excitation efficiency of the chromium tube, whilst providing an equivalent heavy element performance.In the past there have been attempts to produce x-ray tubes combining the properties of both light and heavy element tubes. An example of this is the dual-target tube which has two preferentially excited targets (anodes) of different materials constructed side-by-side.