Review of absolute doubly differential cross-section experiments and cross-section ratios for electron bremsstrahlung from rare gas atom and thin-film targets

We discuss doubly differential cross-section experiments for electron bremsstrahlung from free gas atom and thin-film targets for electron energies of 100 keV or less. We compare cross-section ratios for different target atoms with two theoretical models: ordinary bremsstrahlung and total bremsstrahlung calculated in the stripping approximation. Ratios of cross sections have been used to improve the comparison between experiment and theory when only relative cross sections are available or when the error in the absolute cross section is large. We also discuss additional background processes that may be more important in gas target experiments.     

Continuous X-rays produced in light-ion–atom collisions

Continuous X-rays produced in light-ion–atom collisions producing continuous backgrounds and therefore determining the detection limit of PIXE, have been experimentally and theoretically studied. It is shown that the experimental results over the wide range of projectile-ion energy from 0.5 to 40 MeV are well explained by four sources of radiative processes: nuclear bremsstrahlung (NB), atomic bremsstrahlung (AB) (or polarization bremsstrahlung), secondary-electron bremsstrahlung (SEB), and quasi-free-electron bremsstrahlung (QFEB).     

Photon polarization and spin asymmetry in the elementary process of bremsstrahlung

Experimental and theoretical results are reviewed concerning the photon polarization and spin asymmetry in the elementary process of bremsstrahlung. In electron–photon coincidence experiments using an unpolarized primary beam (300 keV) the electron–nucleus bremsstrahlung was found to be almost completely linearly polarized. The same behavior was found in electron–electron bremsstrahlung. By using a transversely polarized electron beam the photon emission asymmetry was measured for fixed direction of the outgoing electrons.     

Comparison of theory and experiment for polarizational bremsstrahlung

Portillo and Quarles have recently observed significant deviations from ordinary bremsstrahlung predictions for bremsstrahlung from gas targets, after not seeing such effects in solids. These deviations are interpreted as an observation of the polarizational bremsstrahlung component. We review previous discussion of this component. No adequate theory is presently available for the angular dependence of the bremsstrahlung cross section being measured in these new experiments. We examine the validity of the simple estimates which Portillo and Quarles have tried to use.     

Zur Optimierung der Bestrahlungsbedingungen im Bremsstrahlfeld des Mikrotrons MT 22 des vik Dubna

In the bremsstrahlung field of the Microtron MT 22, copper foils (0.035 mm thick) positioned along beam direction and also perpendicular to the beam at different distances from the bremsstrahlung target were irradiated. From these activated copper foils autorodiograms were prepared. By means of a densitron and a microdensitometer, the autoradiograms were measured. The densitron pictures give a qualitative impression of the geometry of the bremsstrahlung field, whereas the curves of optical density yield quantitative values. From optical density curves, conclusions have been drawn about optimal geometry for irradiation positions of samples in this bremsstrahlung field. A sample rotating device applicable for photon activation analysis by means of the MT 22 is described.      

Neutron activation experiments for bremsstrahlung characterization studies

Activation experiments were conducted to assess the bremsstrahlung continuum produced from the activation of the ⁷Li isotope and the subsequent short-lived 13 MeV beta decay of ⁸Li (T _1/2 = 843 ms). The combination of the high energy beta-decay and the high atomic numbered metals used in piping for ⁷Li liquid metal coolants is a scenario in which bremsstrahlung production is a principal shielding concern. A series of fast pneumatic activation experiments have been performed to obtain the spectral distributions of bremsstrahlung gamma-rays transmitted through stainless steel shield samples. Detectors were used in both pulse-height and multichannel scaling analysis modes for energy spectra determination and half-life verification, respectively. Experimental results were utilized to validate the electron transport and bremsstrahlung production models used in the Monte Carlo MCNP code.     

Absorbed dose distributions in a tissue-equivalent absorber for bremsstrahlung produced at the beamlines of the European Synchrotron Radiation Facility

The absorbed-dose distributions for bremsstrahlung, incident on a tissue-equivalent phantom, were measured with LiF : Mg,Ti thermoluminescent dosimeters at two insertion device beamlines of the European Synchrotron Radiation Facility (ESRF). The measurements were carried out for two different electron beam energies of 4 and 6 GeV. The corresponding bremsstrahlung spectra and power were measured using a high-resolution lead glass total absorption calorimeter. The results are compared with similar measurements carried out at other facilities. The normalized bremsstrahlung absorbed dose in a cross-sectional area of 100 mm², at a depth of 150 mm of the phantom, was measured as 6.1 and 3.6 kGy h⁻¹ W⁻¹ for the corresponding bremsstrahlung spectra of 4  and 6 GeV.     

Particle beam sample introduction into glow discharge plasmas for speciation analysis

This paper reviews the use of the particle beam (PB) as a transport-type interface for the introduction of liquid samples into glow discharge (GD) plasmas. Emphasis is placed on the PB interface as a coupling for liquid chromatography (LC) with optical emission spectroscopy (OES) and mass spectrometry (MS) detection methods. Advantages and disadvantages of the particle beam sample introduction for LC–MS and LC–OES as well as a comparison with other interfaces (i.e. moving belt) are covered. Fundamental aspects of the particle beam such as solvent removal and analyte delivery are highlighted. Furthermore, the development of the particle beam interface is discussed regarding its potential for providing “comprehensive speciation” analysis of solution-phase samples. Specifically, the particle beam/hollow cathode–optical emission spectroscopy (PB/HC–OES) technique provides information towards metal and non-metals determinations as well molecular species identification of organic compounds, organometallics, and small biomolecules via empirical formulae determinations. Particle beam–glow discharge mass spectrometry (PB/GDMS) also provides molecular species information through fragmentation pattern analysis of plasma-produced mass spectra that are similar in structure to electron impact (EI) sources. The evolving capabilities of the PB/GD couplings deliver analytical information that is not available from any other spectrochemical source. The technique has relevance to an incredible range of analytical applications and warrants further investigation by other researchers and instrument manufacturers.     

The Application of Complex Wavelet Transform to Spectral Signals Background Deduction

The accuracy of spectrograms may be affected by baseline excursion or drift when infrared spectrometers are used in the analyses of gases. Background deduction or baseline correction is one of the effective pretreatment methods that can improve measurement accuracy. This paper presents a novel methodology based on complex wavelet transform algorithm to perform background deduction. The complex wavelet transform methodology establishes a complex wavelet filter to decompose the spectral signals first, and set the decomposition coefficients in the high-frequency section to zero, and then reconstruct the background signals; finally, the background deduction can be realized by deducting the background signals. In this study, the complex wavelet established by Daubechies was selected to demonstrate background deduction aiming at simulative spectral signals with different backgrounds and the real spectral signal of SF6 decomposition gases. Compared with the results done by the real wavelet transform in the same conditions, the results indicate that complex wavelet transform methodology can perform background deduction more efficiently than real wavelet transform methodology, thus improving the effectiveness and precision of spectrogram measurements greatly, which is useful for SF6 gas decomposition compositions analysis

     

Target thickness dependence of bremsstrahlung from solid films

We report initial results of a study of the target thickness dependence of bremsstrahlung from solid film targets. The electron beam energy is 50 keV and bremsstrahlung is observed at 90°. Targets are aluminium and gold. Target thicknesses from 50 μg/cm², where single interaction conditions apply, to twice the electron range, where a multiple interaction model applies, were studied. We observe the transition from thin to thick film spectra. The purpose is to investigate whether the polarization bremsstrahlung contribution may be suppressed in solid film targets.     

Electron–positron pair production and bremsstrahlung at intermediate energies in the field of heavy atoms

The Coulomb corrections (CC) to the processes of bremsstrahlung and pair production are investigated. The next-to-leading term in the high-energy asymptotics is found. This term becomes very essential in the region of intermediate energies. The influence of screening for CC is small for differential cross section, spectrum, and the total cross section of pair production. The same is true for the spectrum of bremsstrahlung, but not for the differential cross section, where the influence of screening can be very large. The corresponding screening corrections as well as the modification of the differential cross section of bremsstrahlung are found. A comparison of our results for the total cross section of pair production with the experimental data available is performed. This comparison has justified our analytical results and allowed to elaborate a simple ansatz for the next-to-leading correction. The influence of the electron beam shape on CC for bremsstrahlung is investigated. It turns out that the differential cross section is very sensitive to this shape.     

Investigation of enhanced ion abundances from a carrier process in high-performance liquid chromatography particle beam mass spectrometry

Enhancements in ion abundances in high-performance liquid chromatography (HPLC) particle beam (PB) mass spectrometry were observed during coelution or when certain substances (e.g., ammonium acetate) were added to the mobile phase during a reverse-phase gradient elution HPLC separation. These enhancements were observed with two commercial PB interfaces and a variety of compounds generally not amenable to separation by gas chromatography. The enhancements are attributed to both improved chromatographic efficiency and a PB carrier process.     

The Application of Complex Wavelet Transform to Spectral Signals Background Deduction

The accuracy of spectrograms may be affected by baseline excursion or drift when infrared spectrometers are used in the analyses of gases. Background deduction or baseline correction is one of the effective pretreatment methods that can improve measurement accuracy. This paper presents a novel methodology based on complex wavelet transform algorithm to perform background deduction. The complex wavelet transform methodology establishes a complex wavelet filter to decompose the spectral signals first, and set the decomposition coefficients in the high-frequency section to zero, and then reconstruct the background signals; finally, the background deduction can be realized by deducting the background signals. In this study, the complex wavelet established by Daubechies was selected to demonstrate background deduction aiming at simulative spectral signals with different backgrounds and the real spectral signal of SF6 decomposition gases. Compared with the results done by the real wavelet transform in the same conditions, the results indicate that complex wavelet transform methodology can perform background deduction more efficiently than real wavelet transform methodology, thus improving the effectiveness and precision of spectrogram measurements greatly, which is useful for SF6 gas decomposition compositions analysis     

Cluster-assistant generation of multiply charged atomic ions in nanosecond laser ionization of seeded methyl iodide beam

The photoionization of methyl iodide beam seeded in argon and helium is studied by time-of-flight mass spectrometry using a 25 ns, 532 nm Nd-YAG laser with intensities in the range of 2 × 10¹⁰–2 × 10¹¹ W/cm². Multiply charged ions of I^q+ (q = 2–3) and C²⁺ with tens of eV kinetic energies have been observed when laser interacts with the middle part of the pulsed molecular beam, whose peak profiles are independent on the laser polarization directions. Strong evidences show that these ions are coming from the Coulomb explosion of multiply charged CH₃I clusters, and laser induced inverse bremsstrahlung absorption of caged electrons plays a key role in the formation of multiply charged ions.     

Differences in PIXE signal-to-noise ratios and detection limits for conducting targets insulated with glass

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.     

Identification of vitamins A, D and E by particle beam liquid chromatography-mass spectrometry

Particle beam (PB) high performance liquid chromatography (HPLC)-mass spectrometry (MS) has been studied to investigate its suitability for the analysis of fat-soluble vitamins, as an example of thermally labile substances. The PB LC-MS system has been used to detect and identify vitamins A, D and E in foods and multi-vitamin preparations. The qualitative performance of the PB interface has been evaluated by an examination of the working parameters. A rapid elution of the vitamins was obtained on a C8 reversed-phase column using an aqueous methanol mobile phase. Analyses have been carried out using both, electron (EI) and chemical (CI) ionization. Positive and negative-ion CI spectra of the compounds are discussed. When PB-MS conditions are optimized, the detection limits for the fat-soluble vitamins tested have been typically in the 0.6–25 ng range when using the selected-ion monitoring technique.     

Synthesis, characterization, and application of metal organic framework nanostructures

The considerable number of important physical properties, including optical, electronic, and magnetic properties, of Prussian blue (PB) analogues have attracted fundamental and industrial interest. Nevertheless, the gas sorption properties of PB coordination compounds were only investigated very recently. In this work, we report the synthesis and gas sorption properties of PB nanocomposites with different size and shape obtained by using poly(vinylpyrrolidone) (PVP), chitosan, and dioctyl sodium sulfosuccinate (AOT) as stabilizers and structure directing agents. All three porous nanocrystals show high and selective CO(2) adsorption over CH(4) or N(2). No distinct relationship was found between the size (or shape) of the nanosorbents and their gas uptake capacities. To our knowledge, this is the first report on the use of PB nanocomposites for CO(2) capture applications.     

Electroanalytical Study of Prussian Blue Modified Glassy Carbon Paste Electrodes

Two types of glassy carbon (GC) powder (i.e., Sigradur K and Sigradur G) have been mixed with mineral oil to obtain glassy carbon paste electrodes (GCPE's). The electrochemical behavior of such electrodes at different percentages of glassy carbon has been evaluated with respect to the electrochemistry of ferricyanide as revealed with cyclic voltammetry and the best paste composition was chosen. GC was then modified with Prussian Blue (PB), mixed at different percentages with unmodified GC and with a fixed amount of mineral oil in order to obtain PB modified glassy carbon paste electrodes (PB‐GCPE's). PB‐GCPE's with different percentages of GC modified with PB (PB‐GC) were compared and the dependence on the amount of PB on their performances was evaluated by studying the parameters of cyclic voltammetry (i.e., current peak, ΔE_p, anodic and cathodic current ratio, charge density) and the amperometric response to H₂O₂. Data interpretation based on the GC surface area is presented. GCPE's with a selected amount of PB‐GC were then tested as H₂O₂ probes and all the analytical parameters together with the dependence on pH were evaluated. Some preliminary experiments with these electrodes assembled as glucose, lysine and lactate biosensors are also reported.     

Formation of the background component of the analytical signal in the long-wavelength region of X-ray fluorescence spectrum

Components of X-ray background in the long-wavelength spectral region of a crystal diffraction X-ray fluorescence spectrometer were calculated. The calculations took into account the bremsstrahlung radiation of free electrons, diffuse scattering and fluorescence of the crystal analyzer, and high-order reflections of the scattered radiation of the fluorescent sample by the crystal analyzer. The results of calculations were compared with the intensities of background samples measured in the region of the NaK _α fluorescence line on an SRM-25 wave X-ray spectrometer. The experimental background intensities (response function) well correlate with those found by the regression equation with calculated factors. The importance of particular processes in the formation of X-ray background was assessed.