| 1. |
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| 2. |
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| 3. |
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| 4. |
- Gustafsson, Jörgen, et al.
(författare)
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The influence of hyperfine structure and isotope shift on the detection of Rb by 2f-wavelength modulation diode laser absorption spectrometry : experimental verification of simulations
- 1998
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 53:14, s. 1895-1905
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Tidskriftsartikel (refereegranskat)abstract
- This work presents an experimental verification of a previously developed methodology for simulation of the 2f-wavelength modulation diode laser absorption spectrometry technique (2f-WM-DLAS) when the influence of hyperfine structure, isotope shift and collisional broadening and shift of an atomic transition is taken into account [J. Gustafsson, D. Rojas and O. Axner, Spectrochim. Acta, 52B, 1937-1953 (1997)]. The pilot element in the simulations was Rb, detected at the 780 nm 5s2 S1/2 - 5p2 P3/2 transition, in low-pressure cells and atmospheric-pressure reservoirs (e.g. graphite furnaces). This experimental investigation verifies that the simulations are able to predict, with good accuracy, experimental 2f-WM signals from Rb atoms under both low-pressure, room-temperature conditions and atmospheric-pressure, high-temperature conditions. This implies that the previously published simulation methodology can be used for predicting and optimizing 2f-WM signal strengths and shapes from Rb atoms (and thereby presumably also from other atoms) under a variety of pressure and temperature conditions.
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| 5. |
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| 6. |
- Boudreau, Denis, et al.
(författare)
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DensMat: fully time-resolved simulation of two-step pulsed laser excitation of atoms in highly collisional media
- 1996
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 51:4, s. 413-428
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Tidskriftsartikel (refereegranskat)abstract
- A program that simulates and displays the level populations of atomic systems exposed to dual-wavelength (i.e. two-colour) pulsed laser excitation in highly collisional media (such as flames and plasmas) has been developed. The program is based upon a previously published fully time-dependent density-matrix model that describes step-wise excitations of atoms with degenerate states under collision-dominated conditions, and which thus goes beyond the rate-equations formalism. This model can predict such phenomena as Rabi flopping and a.c.-Stark splitting, shifting and broadening. The program can be used as a prediction tool for laser-enhanced ionization, laser-induced fluorescence, fluorescence dip spectroscopy and other two-colour laser-based spectroscopic experiments. The program provides the user with a flexible four-level atomic system, configurable as a one- or two-step excitation ladder, along with an ionization continuum and non-laser-connected level(s) that may act as trap(s) or metastable level(s). Parameters such as level degeneracy, collisional rates and laser pulse widths, shapes, wavelengths, intensities and bandwidths are accessible to the user. The program can display both the time development of the level populations and also level populations versus laser wavelength. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by a disk containing the program DensMat, an associated on-line help file and manual, an installation program, and data files pertaining to the examples illustrated in this article. The program runs under Windows 3.1 on an IBM-compatible computer.
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| 7. |
- Boudreau, Denis, et al.
(författare)
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The use of DensMat to model stimulated Raman adiabatic passage processes in atoms
- 2001
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 56:9, s. 1787-1795
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Tidskriftsartikel (refereegranskat)abstract
- Stimulated Raman Adiabatic Passage (STIRAP) is a technique that is capable of transferring an almost entire atomic or molecular population from one quantum level to another by a coherent two-step excitation process. The most remarkable property of this technique is that it is applicable to situations in which the intermediate atomic or molecular state is exposed to a large loss rate. However, the STIRAP process has not yet been used for laser spectrochemical analysis. As a part of the ongoing development of new laser-based spectrometric techniques, this article demonstrates how a previously published simulation program, DensMat, can be used to model STIRAP processes in atoms under various collisional and laser bandwidth conditions.
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| 8. |
- Chekalin, Nikolai, et al.
(författare)
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Laser-induced fluorescence in graphite furnaces under low pressure conditions as a powerful technique for studies of atomization mechanisms : investigation of Ag
- 1994
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 49:12-14, s. 1411-1435
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Tidskriftsartikel (refereegranskat)abstract
- A new method for accurate studies of atomization processes of various elements in graphite furnaces has been developed. It utilizes the highly sensitive Laser-Induced Fluorescence spectrometry technique for detection of atoms in Graphite Furnaces under Low Pressure conditions (LIF-GF-LP). The high sensitivity of the LIF technique enables the study of atomization processes at low pressures under true analytical conditions (i.e. for low analyte mass) with a minimum of influences from diffusion processes. This first work is concerned with an investigation of the atomization mechanisms of Ag. It was found that the LIF-GF signal area was linear with pressure for virtually all pressures. The LIF-GF signal shape (versus time as well as versus 1/T) was found to vary with both pressure and concentration. The signals were, in general, found to have a shorter duration and higher appearance and peak temperatures, the higher the pressure. Activation energies could be evaluated from the LIF-GF-LP curves very accurately by the Smets method. Excellent agreements with the predicted linear relationship were obtained for a major part of the signal curve (> 50%) under many sample and furnace conditions. Studies of the activation energy dependence on pressure, analyte mass and heating rate gave valuable information about the atomization mechanisms of Ag in graphite furnaces. The findings support a picture that Ag atomizes as individual adatoms under low pressure and low analyte mass conditions. Under atmospheric conditions, repeated desorption and adsorption processes delay the appearance of the signal in time as well as being responsible for formation of 2-D and 3-D microstructures on the surface.
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| 9. |
- Gustafsson, Jörgen, et al.
(författare)
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Improved detectability of wavelength modulation diode laser absorption spectrometry applied to window-equipped graphite furnaces by 4th and 6th harmonic detection
- 2003
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 58:1, s. 111-122
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Tidskriftsartikel (refereegranskat)abstract
- Wavelength modulation-diode laser absorption spectrometry (WM-DLAS) is a technique for sensitive detection of atoms and molecules in gas phase, whose detectability often has been found to be limited by background signals originating from multiple reflections between surfaces in optical components, so-called etalon effects. This work investigates the dependence of the detectability of the WM-DLAS technique on the order of the harmonic detected when the technique is combined with a window-equipped graphite furnace (GF). It is shown that although the analytical WM-signal, SrAS,nf, for a particular detection order, n, is decreasing with increased detection order, i.e. SrAS,2f>SrAS,4f>SrAS,6f, the signal-to-background ratio, (SrAS/SrBG)nf, and thereby also the detectability, are related in the reverse order, i.e. as (SrAS/SrBG)6f≫(SrAS/SrBG)4f≫(SrAS/SrBG)2f. This implies that it is more advantageous to detect higher even order components, e.g. the 4th or the 6th, than the 2nd when the WM-DLAS technique is applied to a window-equipped GF.
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| 10. |
- Gustafsson, Jörgen, et al.
(författare)
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Theoretical investigation of the temperature dependence of the 2f-wavelength modulated diode-laser absorption signal
- 1998
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 53:13, s. 1827-1846
-
Tidskriftsartikel (refereegranskat)abstract
- The temperature dependence of 2f-wavelength modulated signals has been investigated theoretically both for single-transition atoms (representing mono-isotopic atoms lacking hyperfine structure) and the 780 nm 12-peak transition in Rb using a previously developed simulation methodology. The temperature dependence, denoted ξ, is defined as the ratio of the relative change of the 2f-signal (ΔS-2f)/S-2f) to that of the temperature (ΔT/T). For small modulation amplitudes, the temperature dependence is plus and minus unity (ξ0L = 1, ξ0G = -1) on resonance of single-transition atoms having Lorentzian and Gaussian broadened transitions and slightly below unity (0.6 < ξ0V < 0.8) for transitions with a Voigt profile under conditions prevailing in a graphite furnace. When optimum modulation amplitudes are used the temperature dependence is smaller (IξI < 0.1) as long as the sample has a low Sample Optical Thickness (SOT), however increasing with increasing SOT (e.g. ξ0V > 1 for SOTs > 8 for a single Voigt broadened transition and ξ0Rb > 1 for SOTs > 12 for the 780 nm transition in Rb). For detuned conditions, ξ can take both larger and smaller values.
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| 11. |
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| 12. |
- Ljung, Per, et al.
(författare)
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Detection of titanium in electrothermal atomizers by laser-induced fluorescence : Part 2. Investigation of various types of atomizers
- 1997
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 52:6, s. 703-716
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Tidskriftsartikel (refereegranskat)abstract
- Different types of electrothermal atomizers (graphite and tungsten furnaces) have been studied for the determination of Ti by laser-induced fluorescence (LIF). It was found that all graphite furnaces suffer from both bulk contamination by Ti, corresponding to tens of pg per firing, and significant memory effects in such a way that the high sensitivity of the LIF technique could not be fully utilized. The detectability of Ti by the LIF technique was limited by fluctuations of the atomizer blank signals and therefore depended mainly on the Ti history of the furnaces. The detection limit of Ti was found to be similar for all graphite furnaces: around 1 pg for furnaces not exposed to any substantial amounts of Ti, and a few pg for those which had been exposed to a few hundreds of pg of Ti (or more). It was found that the transversely heated graphite atomizer (THGA) from Perkin-Elmer gives the most reproducible atomization of Ti.The tungsten furnace showed no memory effects and therefore no empty firings (burn-outs) between determinations are needed. The tungsten furnace, however, afforded significantly weaker signals (approximately 250-fold) than the graphite furnaces; this was attributed to incomplete atomization processes. The Ti signal from the tungsten furnace could be increased by the addition of H2 in the buffer gas. For 20% of H2 added, however, the analyte signal was still weaker by a factor of 8 than that seen in a graphite furnace shielded with Ar (the remaining difference is primarily attributed to fluorescence quenching from H2) In addition, the precision of the measurements was poorer than that obtained from graphite furnaces.
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| 13. |
- Ljung, Per, et al.
(författare)
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Detection of titanium in electrothermal atomizers by laser-induced fluorescence : Part 1. Determination of optimum excitation and detection wavelengths
- 1997
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 52:6, s. 675-701
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Tidskriftsartikel (refereegranskat)abstract
- A detailed investigation has been performed of suitable excitation and detection wavelengths of Ti for the technique of laser-induced fluorescence in electrothermal atomizers. Fluorescence spectra (most often in the 250-350 nm region) from the 39 excitation wavelengths conjectured to be the most important (in the 220-270 nm region) have been investigated in more detail by the use of an intensified CCD detector. The fluorescence spectra were found to have a rich occurrence of peaks (about 50 each), of which many cannot be found in existing atomic wavelength data in the literature. All of the peaks found (with one exception) could be identified thanks to a home-made program that calculates atomic wavelengths from existing energy level data. Most of the spectra are dominated by ''indirect'' transitions (i.e. fluorescence from an upper level that is different from the one accessed by the laser) despite the prediction of existing ''direct'' transitions. This indicates that the collisional redistribution processes amongst the excited levels, in general, are faster than typical fluorescence rates for Ti in graphite furnaces. Suitable excitation and detection wavelength combinations are given. One such suitable choice is excitation at 264.662 nm since the fluorescence following this excitation consisted of peaks of almost equal magnitude in three different wavelength regions (around 295, 319 and 338 nm).
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| 14. |
- Ljung, Per, et al.
(författare)
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Measurements of rubidium in standard reference samples by wavelength-modulation diode laser absorption spectrometry in a graphite furnace
- 1997
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 52:3, s. 305-319
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of the capabilities of the WM-LDAS-GF (wavelength-modulation laser diode absorption spectrometry in graphite furnaces) technique for detection of Rb at low pg ml-1 concentrations in samples with complex matrices has been performed. Five reference materials were investigated with respect to their Rb content by the WM-LDAS-GF technique: corn bran (NIST 8433); NIST water; (1643d) riverine water (SLRS-2); estuarine water (SLEW-1); and sea water (NASS-3). Freeze-dried corn bran was found to have a Rb concentration of 440 ± 70 ng g-1. This compares well with the certified concentration of 500 ± 300 ng g-1. The Rb content of the MST water was assessed to 12.7 ± 1.7 ng ml-1. This compares excellently with the specified (although not certified) level of 13 ng ml-1. None of the three other reference materials has any certified Rb level. The Rb content of riverine water was found to be 3.4 ± 0.8 ng ml-1. Chemical interferences were encountered when estuarine water and sea water were analyzed (loss of Rb as RbCl). Addition of NH4NO3 as the matrix modifier increased the Rb recovery values considerably (although not fully to unity). Estuarine water and sea water were found to have Rb contents of 30 ± 10 ng ml-1 and 140 ± 50 ng ml-1, respectively. A detection limit for Rb in deionized water of 10 fg (corresponding to a concentration of 1 pg ml-1 using a 10 μL aliquot) was obtained. This is identical to (and thus verifies) the previously published result by the group of K. Niemax. These results show that the WM-LDAS-GF technique is capable of detecting traces of Rb in samples also with complex matrices.
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| 15. |
- Marunkov, Alexander, et al.
(författare)
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Detection of trace amounts of Ni by laser-induced fluorescence in graphite furnace with intensified charge coupled device
- 1994
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 49:12-14, s. 1385-1410
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Tidskriftsartikel (refereegranskat)abstract
- A laser-induced fluorescence in graphite furnace (LIF-GF) set-up has been equipped with an intensified CCD detector (ICCD) that enables simultaneous multichannel detection of large wavelength regions. The main advantages of such a system in comparison with conventional photomultiplier detection are: simultaneous detection of several fluorescence wavelengths for easy characterization of excitation and fluorescence spectra and for an increase of the absolute sensitivity and spectral selectivity; simultaneous monitoring of background signals, such as those due to matrix interferences, blackbody radiation and scattered laser light; decrease of the susceptibility to radio-frequency pick-ups emitted from the pump laser due to the delayed read-out procedure; time-resolved studies of fluorescence spectra for improved elemental selectivity or for studies of atomization processes, and a possibility to perform two-dimensional imaging of height distributions of atomization and, in combination with an imaging spectrometer. diffusion processes in the furnace. The first work on LIF-GF with ICCD detection has been performed on Ni. The most sensitive and versatile excitation and detection wavelengths have been identified. Detection limits in water solutions by the LIF-GF technique have been improved by two orders of magnitude and are found to be 0.015 pg with ICCD and 0.01 pg using a photomultiplier at the most sensitive excitation and detection wavelengths. Nickel in ng/ml concentrations has been detected in aqueous standard reference samples with sodium concentrations ranging from μg/ml to % (riverine water and estuarine water) with good accuracy and precision. The Ni contents of standard riverine and estuarine water were determined to 1.00 +/- 0.11 and 0.75 +/- 0.07 ng/m
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| 16. |
- Rojas, Dorys, et al.
(författare)
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An investigation of the 2f—wavelength modulation technique for detection of atoms under optically thin as well as thick conditions
- 1997
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 52:11, s. 1663-1686
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of the 2f-wavelength modulation (WM) technique for detection of atoms under optically thin as well as thick conditions is presented. A program that simulates the entire process of laser light modulation, atomic absorption and signal demodulation has been constructed. The dependence of the 2f-WM signal upon frequency amplitude modulation and detuning for a variety of atomic masses (i.e. optical densities) is investigated in detail. It is shown, among other things, that the 2f-WM (S(bar)2f-r) signal strength is either a dual-or a quadrupled valued function of optical density. Despite this, it shown that the 2f-WM technique can be used, by suitable choices of the frequency amplitude modulation and detuning, for detection of atoms also under optically thick conditions.
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| 17. |
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| 18. |
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| 19. |
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| 20. |
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| 21. |
- Axner, Ove, et al.
(författare)
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A discussion about the significance of absorbance and sample optical thickness in conventional absorption spectrometry and wavelength-modulated laser absorption spectrometry
- 2003
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 58:11, s. 1997-2014
-
Tidskriftsartikel (refereegranskat)abstract
- One of the most frequently used concepts in atomic absorption spectrometry (AAS) is that of Absorbance, an easily measurable quantity that is linear with the concentration of the analyte over a large range of concentrations whenever Beer's law is valid. Laser-based modulation techniques, however, in particular wavelength modulated diode laser absorption spectrometry (WMAS), do not measure exactly the same physical quantities as conventional AAS techniques do, since they do not rely upon separate measurements of the intensities in the presence and in the absence of the sample, but rather (a certain fraction of) the difference between the signals 'on' and 'off' resonance. Hence, Absorbance is not as natural for the modulated laser-based absorption techniques as it is for the conventional AAS techniques. The entity called sample optical thickness (SOT) appears to be a natural entity as well as a natural unit (denoted SOT units) for the quantification of signals in WMAS. The present paper discusses the concept of measurable quantities and their units in WMAS in some detail and compares them (theoretical and practical considerations) with those of conventional AAS. In particular, it makes a distinction between the 'observed' sample optical thickness and the 'true' sample optical thickness and shows how these two entities are related to the Absorbance entity. Finally, this work also introduces a dimensionless sensitivity of the WMAS technique, and shows this quantity to be equal to the nth Fourier coefficient of the wavelength modulated, peak-normalized line shape function.
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| 22. |
- Axner, Ove, et al.
(författare)
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Assessment of gas molar density by gas modulation refractometry : A review of its basic operating principles and extraordinary performance
- 2021
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier B.V.. - 0584-8547 .- 1873-3565. ; 179
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Tidskriftsartikel (refereegranskat)abstract
- A technique for high-precision and high-accuracy assessment of both gas molar (and number) density and pressure, Gas Modulation Refractometry (GAMOR), is presented. The technique achieves its properties by assessing refractivity as a shift of a directly measurable beat frequency by use of Fabry-Perot cavity (FPC) based refractometry utilizing the Pound-Drever-Hall laser locking technique. Conventional FPC-based refractometry is, however, often limited by fluctuations and drifts of the FPC. GAMOR remedies this by an additional utilization of a gas modulation methodology, built upon a repeated filling and evacuation of the measurement cavity together with an interpolation of the empty cavity responses. The procedure has demonstrated an ability to reduce the influence of drifts in a non-temperature stabilized dual-FPC (DFPC)-based refractometry system, when assessing pressure, by more than three orders of magnitude. When applied to a DFPC system with active temperature stabilization, it has demonstrated, for assessment of pressure of N2 at 4304 Pa at room temperature, which corresponds to a gas molar density of 1.7 × 10−6 mol/cm3, a sub-0.1 ppm precision (i.e. a resolution of 0.34 mPa). It is claimed that the ability to assess gas molar density is at least as good as so far has been demonstrated for pressure (i.e. for the molar density addressed, a resolution of at least 1.2 × 10−13 mol/cm3). It has recently been argued that the methodology should be capable of providing an accuracy that is in the low ppm range. These levels of precision and accuracy are unprecedented among laser-based techniques for detection of atomic and molecular species. Since the molar polarizability of He can be calculated by ab initio quantum mechanical calculations with sub-ppm accuracy, it can also be used as a primary or semi-primary standard of both gas molar (and number) density and pressure. © 2021 The Author(s)
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| 23. |
- Axner, Ove, et al.
(författare)
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Authors’ reply
- 2004
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Ingår i: Spectrochimica Acta, Part B. ; 59:3, s. 390-392
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Tidskriftsartikel (refereegranskat)
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| 24. |
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| 25. |
- Axner, Ove, 1957-, et al.
(författare)
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Noise-immune cavity-enhanced analytical atomic spectrometry — NICE-AAS : a technique for detection of elements down to zeptogram amounts
- 2014
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 100, s. 211-235
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Tidskriftsartikel (refereegranskat)abstract
- Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is a powerful technique for detection of molecular compounds in gas phase that is based on a combination of two important concepts: frequency modulation spectroscopy (FMS) for reduction of noise, and cavity enhancement, for prolongation of the interaction length between the light and the sample. Due to its unique properties, it has demonstrated unparalleled detection sensitivity when it comes to detection of molecular constituents in the gas phase. However, despite these, it has so far not been used for detection of atoms, i.e. for elemental analysis. The present work presents an assessment of the expected performance of Doppler-broadened (Db) NICE-OHMS for analytical atomic spectrometry, then referred to as noise-immune cavity-enhanced analytical atomic spectrometry (NICE-AAS). After a description of the basic principles of Db-NICE-OHMS, the modulation and detection conditions for optimum performance are identified. Based on a previous demonstrated detection sensitivity of Db-NICE-OHMS of 5×10−12 cm−1 Hz−1∕2 (corresponding to a single-pass absorbance of 7×10−11 over 10 s), the expected limits of detection (LODs) of Hg and Na by NICE-AAS are estimated. Hg is assumed to be detected in gas phase directly while Na is considered to be atomized in a graphite furnace (GF) prior to detection. It is shown that in the absence of spectral interferences, contaminated sample compartments, and optical saturation, it should be feasible to detect Hg down to 10 zg/cm3 (10 fg/m3 or 10-5 ng/m3), which corresponds to 25 atoms/cm3, and Na down to 0.5 zg (zg = zeptogram = 10-21 g), representing 50 zg/mL (parts-per-sextillion, pps, 1:1021) in liquid solution (assuming a sample of 10 µL) or solely 15 atoms injected into the GF, respectively. These LODs are several orders of magnitude lower (better) than any previous laser-based absorption technique previously has demonstrated under atmospheric pressure conditions. It is prophesied that NICE-AAS could provide such high detection sensitivity that the instrumentation should not, by itself, be the limiting factor of an assessment of elemental abundance; the accuracy of an assessment would then instead be limited by concomitant species, e.g. originating from the handling procedures of the sample or the environment.
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| 26. |
- Bengtson, Arne
(författare)
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LIBS compared with conventional plasma optical emission techniques for the analysis of metals – A review of applications and analytical performance
- 2017
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier BV. - 0584-8547 .- 1873-3565. ; 134, s. 123-132
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Tidskriftsartikel (refereegranskat)abstract
- This review is focused on a comparison of LIBS with the two most common plasma Optical Emission Spectroscopy (OES) techniques for analysis of metals; spark OES and glow discharge (GD) OES. It is shown that these two techniques have only minor differences in analytical performance. An important part of the paper reviews a direct comparison of the analytical figures of merit for bulk analysis of steels using spark and LIBS sources. The comparison was carried out using one instrument with interchangeable sources, eliminating differences related to the optical system and detectors. It was found that the spark provides slightly better analytical figures of merit. The spark analysis is considerably faster, the simple design of the spark stand has enabled complete automation, both properties of great importance in the metallurgical industry for routine analysis. The analysis of non-metallic inclusions (NMI) with spark and LIBS is presented, in the case of the spark this has become known as Pulse Distribution Analysis (PDA). A very significant difference between the techniques is that the electrical spark typically evaporates ~ 100 times more material than a single laser pulse, resulting in complete evaporation of an NMI present in the evaporated metal. The major advantage of LIBS is that it is localised with very good lateral resolution. The major advantages of spark is that it is much faster (can be done simultaneous with the bulk analysis) and easier to quantify. Compositional Depth Profiling (CDP) is compared for GD-OES and LIBS. It is shown that for applications where GD-OES is well suited, e.g. coated metallic sheet, GD-OES still performs slightly better than LIBS. Similar to the case of NMI analysis, the major advantage of LIBS is the great lateral resolution. This allows elemental surface mapping, as well as CDP of very small areas on μm scale. One further advantage of LIBS is that samples of almost any material, shape and size can be analysed, whereas GD-OES has only limited capabilities for non-flat and small samples. A general conclusion of this review is that LIBS is not likely to replace spark and GD-OES in the foreseeable future, for applications where these techniques are well suited. On the other hand several new applications, particularly in the field of on-line monitoring of industrial processes, are making great inroads for LIBS in the metallurgical and manufacturing industries.
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| 27. |
- Błachucki, Wojciech, et al.
(författare)
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High energy resolution off-resonant spectroscopy : A review
- 2017
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier BV. - 0584-8547 .- 1873-3565. ; 136:Supplement C, s. 23-33
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Forskningsöversikt (refereegranskat)abstract
- We review the high energy resolution off-resonant spectroscopy (HEROS) technique. HEROS probes the unoccupied electronic states of matter in a single-shot manner thanks to the combination of off-resonant excitation around atomic core states using wavelength dispersive X-ray detection setups. In this review we provide a general introduction to the field of X-ray spectroscopy together with the specification of the available X-ray techniques and X-ray methodologies. Next, the theoretical description of the HEROS approach is introduced with a special focus on the derivation of the X-ray emission and X-ray absorption correspondence relation at off-resonant excitation conditions. Finally, a number of experimental HEROS reports are reviewed in the field of chemistry and material science. We emphasize the applicability of HEROS to pulsed X-ray sources, like X-ray free electron lasers, and support the review with experimental examples. The review is complemented with perspectives on and possible further applications of the HEROS technique to the field of X-ray science.
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| 28. |
- Boman, Johan, 1955, et al.
(författare)
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Trace elements in PM2.5 in Gothenburg, Sweden
- 2010
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Ingår i: Spectrochimica Acta - Part B: Atomic Spectroscopy. - : Elsevier BV. - 0584-8547. ; 65:6, s. 478-482
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Tidskriftsartikel (refereegranskat)abstract
- Ambient aerosol particles smaller than 2.5 µm (PM2.5) are getting more and more attention worldwide. While legal focus is mainly on sample mass, the composition of the particles is an important research field gaining increased interest. The interest is not only connected to possible health effects of the elemental content of the particles, but the elemental determination can also add valuable information for source apportionment. Samples were collected during 20 days in November 2007 at the campus of the Chemistry Department, University of Gothenburg, Gothenburg, Sweden. The particles were collected using a cyclone that separates the PM2.5 particles from the air stream and impacts them on polycarbonate filters. Filters were changed at early afternoon. The samples were analyzed for particulate mass, black carbon (BC) and the elements S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, As, Br, Cd and Pb. Several of the elements were above detection limit in only a few of the samples. Total reflection X-ray fluorescence (TXRF) spectrometer based on the Wobi TXRF module supplied by the International Atom Energy Agency (IAEA) has been used for the determination of most trace elements in the samples. A Graphite Furnace Atomic Absorption Spectrometer (GF-AAS) was used for complementary trace element analysis and a reflectometer was used to analyze black carbon. Before elemental analysis the filters were digested using a microwave digestion system with temperature and pressure control. The results showed a large variation in sample mass, BC and analyzed elemental concentrations. The variation of the different constituents did not show the same pattern. This added to the picture of different sources for different pollutants. The highest S concentration was noted on a day when the air masses were determined to come from the southeast, i.e. Poland and some other Eastern European countries. From the results it can be concluded that more work is needed on the TXRF spectrometer to optimize it for determination of the EU legally regulated elements As, Ni, Pb and Cd. Despite this the study shows that there is no problem in meeting the AAQS limits for Cd and Pb in Gothenburg.
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| 29. |
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| 30. |
- Ek, Sara, et al.
(författare)
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Compact fiber-optic fluorosensor employing light-emitting ultraviolet diodes as excitation sources
- 2008
-
Ingår i: Spectrochimica Acta, Part B: Atomic Spectroscopy. - : Elsevier BV. - 0584-8547. ; 63, s. 349-353
-
Tidskriftsartikel (refereegranskat)abstract
- A compact fluorosensor using three different ultraviolet light-emission diodes as excitation sources for fiber-optic recording of fluorescence 10 spectra from samples is described. A compact integrated spectrometer with linear array wavelength recording is used, yielding a spectral resolution 11 of about 8 nm. In two system implementations ultraviolet light-emitting diodes at 300, 340 and 395 nm, or at 360, 385 and 410 nm were used as 12 excitation sources with typical emission halfwidths of 12 nm, each combined with a matching long-path colored-glass filter automatically brought 13 into the fluorescence light flow for suppression of reflected light. Spectra from measurements on vegetation, human skin tumors and a rare-earth 14 ion-based thermographic phosphor were recorded to illustrate the system performance. 15 © 2007 Published by Elsevier B.V.
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| 31. |
- Filella, Montserrat, et al.
(författare)
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A concise guide for the determination of less-studied technology-critical elements (Nb, Ta, Ga, In, Ge, Te) by inductively coupled plasma mass spectrometry in environmental samples
- 2018
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 141, s. 80-84
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing demand for analytical techniques able to measure so-called ‘technology-critical elements’, a set of chemical elements increasingly used in technological applications, in environmental matrices. Nowadays, inductively coupled plasma-mass spectrometry (ICP-MS) has become the technique of choice for measuring trace element concentrations. However, its application is often less straightforward than often assumed. The hints and drawbacks of ICP-MS application to the measurement of a set of less-studied technology-critical elements (Nb, Ta, Ga, In, Ge and Te) is discussed here and concise guidelines given.
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| 32. |
- Geladi, Paul, et al.
(författare)
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Chemometrics in spectroscopy : Part 2. Examples
- 2004
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Ingår i: SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY. - : Elsevier BV. - 0584-8547. ; 59:9, s. 1347-57
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Tidskriftsartikel (refereegranskat)abstract
- Some of the principles and main methods of chemometrics are illustrated by examples. The examples are from electrochemistry, process analytical chemistry and multivariate imaging. Principal component analysis, partial least squares regression and multivariate image analysis are used to illustrate the power of chemometrical thinking. The emphasis is on plotting and visualization for showing the salient features of a model or data set.
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| 33. |
- Gurell, J., et al.
(författare)
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Laser induced breakdown spectroscopy for fast elemental analysis sorting of metallic scrap pieces using certified reference materials
- 2012
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Ingår i: Spectrochimica Acta Part B: Atomic Spectroscopy. - : Elsevier BV. - 0584-8547. ; 74, s. 46-50
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Tidskriftsartikel (refereegranskat)abstract
- A setup utilizing laser induced breakdown spectroscopy (LIBS) for performing elemental analysis in order to classify metallic samples is currently under construction. The setup uses short laser pulses to locally ablate the sample create luminous plasmas. The emitted light is analyzed spectroscopically for instantaneous determination of the elemental composition. A table-top system based on a compact CCD spectrometer has been constructed combined with fast software in order to test the concept of remote, single shot material classification with LIBS. Certified reference materials with known elemental compositions were used in the laboratory tests. We report on successful laboratory tests in which samples were classified using an analysis based on optical emission following a single laser pulse with an operating distance of approximately 1 m. Details regarding field tests of this versatile promising technique are discussed.
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| 34. |
- Gustafsson, Jörgen, et al.
(författare)
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Double modulation diode laser absorption spectrometry by simultaneous wavelength modulation and optically induced population modulation : application to trace element detection in window-equipped graphite furnaces
- 2004
-
Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - Oxford : Pergamon P.. - 0584-8547 .- 1873-3565. ; 59:1, s. 67-92
-
Tidskriftsartikel (refereegranskat)abstract
- A new diode laser-based double modulation absorption spectrometry (DMAS) technique for detection of species in trace amounts/concentrations is presented. The new technique makes use of a simultaneous modulation of the wavelength and population in order to reduce the background signals from multiple reflections in optical components (so-called etalon effects) that normally appear in ordinary wavelength modulation absorption spectrometry (WMAS). The simultaneous wavelength and population modulation are achieved by splitting the light from a wavelength-modulated diode laser into two beams—one strong pump beam and one weak probe beam—that subsequently are overlapped in an interaction region inside a sample compartment. The objective of the pump beam is to periodically transfer population from the state with which the probe beam interacts. The modulation of the population is achieved by modulating the pump beam with a chopper. The transmission of the probe beam is detected and demodulated at a frequency that is a combination of various harmonics of the wavelength modulation and chopping frequencies. The purely optical modulation makes the new technique more generally applicable than other DMAS techniques. The new DMAS technique is thoroughly described by a Fourier series-based theoretical description that previously has shown to be powerful for description of WMAS. The theoretical description is general in the sense that it considers DMAS for a variety of modes of operation and for any sample compartment providing homogeneously broadened transitions. The experiments were carried out on the 780-nm transition in Rb in a window-equipped graphite furnace (GF) used as an atomizer for aqueous solutions of Rb in ppt concentrations. The limit of detection obtained for the DMAS technique applied to a window-equipped GF was more than an order of magnitude better than that for the ordinary WMAS technique applied to the same type of window-equipped GF, and similar to that from an ordinary WMAS instrumentation coupled to a window-less GF, i.e. approximately 10 fg. Since the analytical DMAS signal was found to be approximately one order of magnitude smaller than the corresponding WMAS signal, it could be concluded that the noise from the background signal from the DMAS technique applied to a window-equipped GF was likewise about one order of magnitude smaller than the noise from ordinary WMAS applied to an open GF system. This implies in turn that the results so far published from the ordinary GF–WMAS technique are not shot noise limited and should therefore in principle also be improvable.
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| 35. |
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| 36. |
- Hallquist, Mattias, 1969, et al.
(författare)
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Analysis of organic substances and trace elements in aerosol samples using Fourier transform infra-red and total reflection X-ray fluorescence methods, initial experiments
- 2004
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Ingår i: Spectrochimica Acta Part B-Atomic Spectroscopy. - : Elsevier BV. - 0584-8547. ; 59:8, s. 1193-1197
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Tidskriftsartikel (refereegranskat)abstract
- The ann of this study was to find a way to analyze trace elements as well as organic functional groups in the same aerosol sample. Size segregated aerosol particles were produced under laboratory conditions. The particles contained known amounts of inorganic and organic compounds and were analyzed using total reflection X-ray fluorescence (TXRF) and Fourier transform infra-red (FTIR) spectroscopy for their inorganic and organic content, respectively. A linear relation was obtained between the inorganic content from the TXRF analysis and specific organic functional groups evaluated by FTIR, although a transfer of the sample from quartz plates to zincselenide plates was necessary. The linear relation can be used for quantification of organic functional groups of other aerosol samples. Further improvements and possible applications of the combined techniques are discussed. (C) 2004 Elsevier B.V. All rights reserved.
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| 37. |
- Hansson, Edvin, et al.
(författare)
-
Uranium aerosols at a nuclear fuel fabrication plant: Characterization using scanning electron microscopy and energy dispersive X-ray spectroscopy
- 2017
-
Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Pergamon Press. - 0584-8547 .- 1873-3565. ; , s. 130-137
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Tidskriftsartikel (refereegranskat)abstract
- Detailed aerosol knowledge is essential in numerous applications, including risk assessment in nuclear industry. Cascade impactor sampling of uranium aerosols in the breathing zone of nuclear operators was carried out at a nuclear fuel fabrication plant. Collected aerosols were evaluated using scanning electron microscopy and energy dispersive X-ray spectroscopy. Imaging revealed remarkable variations in aerosol morphology at the different workshops, and a presence of very large particles (up to ≅ 100 × 50 μm2) in the operator breathing zone. Characteristic X-ray analysis showed varying uranium weight percentages of aerosols and, frequently, traces of nitrogen, fluorine and iron. The analysis method, in combination with cascade impactor sampling, can be a powerful tool for characterization of aerosols. The uranium aerosol source term for risk assessment in nuclear fuel fabrication appears to be highly complex.
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| 38. |
- Hermann, G, et al.
(författare)
-
Platform-to-platform sample transfer, distribution, dilution, and dosing via electrothermal vaporization and electrostatic deposition
- 2004
-
Ingår i: Spectrochimica Acta Part B: Atomic Spectroscopy. - : Elsevier BV. - 0584-8547. ; 59:5, s. 737-48
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Tidskriftsartikel (refereegranskat)abstract
- A novel system for solid sample pretreatment, handling and dosing for analytical atomic spectrometry is described. A primary solid or liquid sample is vaporized in a graphite furnace and then condensed in a specially designed condensation zone. On the further transport path, the analyte aerosol can be diluted and distributed in pre-set ratios in the laboratory made flow control system. Applying a corona discharge, aerosol particulates are then quantitatively re-collected by means of intra-furnace electrostatic precipitation on the platform of another graphite furnace or by external precipitation on one or a set of platforms. This makes possible to produce a set of secondary platforms with equal analyte compositions from one individual primary sample. Such multitudes allow sequential multi-element determinations with single-element instrumentation or comparative measurements with different techniques. Furthermore, the described procedure allows external thermal sample pretreatment with preceding pyrolysis and additional vaporization, condensation, and re-precipitation that significantly reduces or removes the sample matrix. Owing to different losses, transport efficiencies of electrothermal vaporization (ETV) instrumentation depend on analyte element, matrix, vaporization temperature, ramp rate, and tube history. In order to reduce the losses and therewith such dependencies of the losses, new laboratory constructed ETV unit with analyte condensation in an axially focusing upstream convection zone has been constructed. Analytical performance of the new setup is compared with the performance of a commercial end-on flow-through ETV unit when analyzing both liquid dosed samples and certified solid reference materials. The new system shows much higher transport efficiencies that are, in addition, more uniform for elements of different volatility. The effects of chemical sample modifiers and elements supporting analyte condensation are studied. Most of the analytical measurements were carried out with a continuum source coherent forward scattering multi-element spectrometer. Comparative measurements were also carried out independently in the co-authors’ laboratories with atomic absorption and inductively coupled plasma mass spectrometry techniques.
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| 39. |
- Holakooei, Parviz, et al.
(författare)
-
On, under and beneath the patina: Evaluation of micro energy dispersive X-ray fluorescence quantitative data on the classification of archaeological copper alloys
- 2021
-
Ingår i: Spectrochimica Acta - Part B Atomic Spectroscopy. - : Elsevier BV. - 0584-8547. ; 178
-
Tidskriftsartikel (refereegranskat)abstract
- A series of quantitative micro X-ray fluorescence (μ-XRF) analyses was performed on a) corroded surface, b) stripped-patina area and c) polished cross section of twenty-five archaeological copper alloys from Iran in order to check the viability of quantitative XRF data for the classification of ancient copper alloys. The limits of detection and quantification and, also, the precision and accuracy of the analytical data were measured using twelve certified reference materials (CRM). The compositional data obtained through these three approaches were statistically evaluated comparing with the compositional data on the same samples obtained by the inductively coupled plasma – optical emission spectroscopy (ICP-OES). We demonstrated that the corroded surfaces are depleted in Ni and Zn and enriched in Pb, Sn and As. Also, we suggest that although μ-XRF quantitative compositional data collected from the corroded surfaces may result in misleading information, the areas with the lowest Sn concentration may represent the closest compositional data to the absolute quantity of Cu, Zn, As and Pb in ancient copper alloys. Moreover, it is shown that the quantitative μ-XRF data obtained from the stripped-patina surface and those from the polished cross sections are comparable with the ICP-OES compositional data and can be confidently used for determining the diversity and technology of ancient copper alloys.
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| 40. |
- Israelsson, Axel, et al.
(författare)
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On the Distribution of Uranium in Hair : Non-Destructive Analysis Using SR-μXRF
- 2015
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Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 108, s. 28-34
-
Tidskriftsartikel (refereegranskat)abstract
- In the present study the distribution of uranium in single human hair shafts has been evaluated using two synchrotron radiation (SR) based micro X-ray fluorescence techniques; SR μ-XRF and confocal SR μ-XRF. The hair shafts originated from persons that have been exposed to elevated uranium concentrations. Two different groups have been studied, i) workers at a nuclear fuel fabrication factory, exposed mainly by inhalation and ii) owners of drilled bedrock wells exposed by ingestion of water. The measurements were carried out on the FLUO beamline at the synchrotron radiation facility ANKA, Karlsruhe. The experiment was optimized to detect U with a beam size of 6.8 μm × 3 μm beam focus allowing detection down to ppb levels of U in 10 s (SR μ-XRF setup) and 70 s (SR confocal μ-XRF setup) measurements. It was found that the uranium was present in a 10–15 μm peripheral layer of the hair shafts for both groups studied. Furthermore, potential external hair contamination was studied by scanning of unwashed hair shafts from the workers. Sites of very high uranium signal were identified as particles containing uranium. Such particles, were also seen in complementary analyses using variable pressure electron microscope coupled with energy dispersive X-ray analyzer (ESEM–EDX). However, the particles were not visible in washed hair shafts.These findings can further increase the understanding of uranium excretion in hair and its potential use as a biomonitor.
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| 41. |
- Jernström, Jussi, et al.
(författare)
-
Characterization and source term assessments of radioactive particles from Marshall Islands using non-destructive analytical techniques
- 2006
-
Ingår i: Spectrochimica Acta, Part B: Atomic Spectroscopy. - : Elsevier BV. - 0584-8547. ; 61, s. 971-979
-
Tidskriftsartikel (refereegranskat)abstract
- Six plutonium-containing particles stemming from Runit Island soil (Marshall Islands) were characterized by non-destructive analytical and microanalytical methods. Composition and elemental distribution in the particles were studied with synchrotron radiation based micro X-ray fluorescence spectrometry. Scanning electron microscope equipped with energy dispersive X-ray detector and with wavelength dispersive system as well as a secondary ion mass spectrometer were used to examine particle surfaces. Based on the elemental composition the particles were divided into two groups: particles with pure Pu matrix, and particles where the plutonium is included in Si/O-rich matrix being more heterogenously distributed. All of the particles were identified as nuclear fuel fragments of exploded weapon components. As containing plutonium with low 240Pu/239Pu atomic ratio, less than 0.065, which corresponds to weapons-grade plutonium or a detonation with low fission yield, the particles were identified to originate from the safety test and low-yield tests conducted in the history of Runit Island. The Si/O-rich particles contained traces of 137Cs (239 + 240Pu/137Cs activity ratio higher than 2500), which indicated that a minor fission process occurred during the explosion. The average 241Am/239Pu atomic ratio in the six particles was 3.7×10−3 ±0.2×10−3 (February 2006), which indicated that plutonium in the different particles had similar age.
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| 42. |
- Jimenez-Ramos, M. C., et al.
(författare)
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A comparison of two micro-beam X-ray emission techniques for actinide elemental distribution in microscopic particles originating from the hydrogen bombs involved in the Palomares (Spain) and Thule (Greenland) accidents
- 2010
-
Ingår i: Spectrochimica Acta, Part B: Atomic Spectroscopy. - : Elsevier BV. - 0584-8547. ; 65:9-10, s. 823-829
-
Tidskriftsartikel (refereegranskat)abstract
- In order to validate and to gain confidence in two micro-beam techniques: particle induced X-ray emission with nuclear microprobe technique (mu-PIXE) and synchrotron radiation induced X-ray fluorescence in a confocal alignment (confocal SR mu-XRF) for characterization of microscopic particles containing actinide elements (mixed plutonium and uranium) a comparative study has been performed. Inter-comparison of the two techniques is essential as the X-ray production cross-sections for U and Pu are different for protons and photons and not well defined in the open literature, especially for Pu. The particles studied consisted of nuclear weapons material, and originate either in the so called Palomares accident in Spain, 1966 or in the Thule accident in Greenland, 1968. In the determination of the average Pu/U mass ratios (not corrected by self-absorption) in the analysed microscopic particles the results from both techniques show a very good agreement. In addition, the suitability of both techniques for the analysis with good resolution (down to a few mu m) of the Pu/U distribution within the particles has been proved. The set of results obtained through both techniques has allowed gaining important information concerning the characterization of the remaining fissile material in the areas affected by the aircraft accidents. This type of information is essential for long-term impact assessments of contaminated sites. (C) 2010 Elsevier B.V. All rights reserved.
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| 43. |
- Lindblom, Magnus, et al.
(författare)
-
High-resolution differential-interference-contrast x-ray zone plates : Design and Fabrication
- 2007
-
Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier BV. - 0584-8547 .- 1873-3565. ; 62:6-7, s. 539-543
-
Tidskriftsartikel (refereegranskat)abstract
- Differential interference contrast is a potentially powerful technique for contrast enhancement in soft X-ray microscopy. We describe the design and fabrication of single-element diffractive optical elements suitable as objectives for high-resolution differential interference contrast microscopy in the water-window spectral range. A one-dimensional pattern calculation followed by an extension to two dimensions results in a pattern resolution of 1 nm, which is well below fabrication accuracy. The same fabrication process as for normal zone plates is applicable, but special care must be taken when converting the calculated pattern to a code for e-beam lithography.
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| 44. |
- Melikechi, N., et al.
(författare)
-
Correcting for variable laser-target distances of laser-induced breakdown spectroscopy measurements with ChemCam using emission lines of Martian dust spectra
- 2014
-
Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier BV. - 0584-8547 .- 1873-3565. ; 96, s. 51-60
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Tidskriftsartikel (refereegranskat)abstract
- As part of the Mars Science Laboratory, the ChemCam instrument acquires remote laser induced breakdown spectra at distances that vary between 1.56 m and 7 m. This variation in distance affects the intensities of the measured LIBS emission lines in non-trivial ways. To determine the behavior of a LIBS emission line with distance, it is necessary to separate the effects of many parameters such as laser energy, laser spot size, target homogeneity, and optical collection efficiency. These parameters may be controlled in a laboratory on Earth but for field applications or in space this is a challenge. In this paper, we show that carefully selected ChemCam LIBS emission lines acquired from the Martian dust can be used to build an internal proxy spectroscopic standard. This in turn, allows for a direct measurement of the effects of the distance of various LIBS emission lines and hence can be used to correct ChemCam LIBS spectra for distance variations. When tested on pre-launch LIBS calibration data acquired under Martian-like conditions and with controlled and well-calibrated targets, this approach yields much improved agreement between targets observed at various distances. This work lays the foundation for future implementation of automated routines to correct ChemCam spectra for differences caused by variable distance.
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| 45. |
- Seton, Ragnar, 1985-, et al.
(författare)
-
A structured evaluation of regression models for predicting CO2 concentration from plasma emission spectra
- 2022
-
Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 194
-
Tidskriftsartikel (refereegranskat)abstract
- This study is an extensive comparison of the predictive performance of a bagging neural network (BANN), partial least squares (PLS) regressor, and a kernel-based, nonlinear PLS (KPLS) regressor, given experimentally obtained CO2-N2-Ar plasma emission spectra. The spectra, 36231 in total, were obtained from controlled gas mixtures with varying CO2 concentrations fed to a stripline split-ring resonator microplasma source and recorded with an UV-NIR, 2 nm resolution spectrometer. The regression methods’ dependence on (i) number of observations used in training, (ii) preprocessing steps, and (iii) feature selection (in this case wavelength ranges) was evaluated by training and testing 60-66 models per method, each with a unique combination of the aforementioned configuration options, and each trained 4 times with random train-test splits. To compare the models a custom metric that compounds R2, Pearson correlation, and a weighted root mean squared relative error was used. The results show that the BANN models outperform both PLS and KPLS, reaching a peak score of 0.873, with the others getting 0.561 and 0.581, respectively, using the (− ∞ , 1] metric. The top performing BANN model was trained without any feature selection or preprocessing, these steps were, however, required for both the best PLS and KPLS models. In a wider perspective, the results show that BANNs are not only suitable as in-place replacements for PLS-based methods, but increase regression model prediction accuracy on low resolution spectra to such an extent that they offer modelling of previously unattainable, nonlinear information contained in emission spectra datasets.
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| 46. |
- Vieitez, Maria Ofelia, et al.
(författare)
-
Elemental analysis of steel scrap metals and minerals by laser-induced breakdown spectroscopy
- 2005
-
Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier BV. - 0584-8547 .- 1873-3565. ; 60:7-8, s. 920-925
-
Tidskriftsartikel (refereegranskat)abstract
- The atomic emission of laser-induced plasma on steel samples has been studied for quantitative elemental analysis. The plasma has been created with 8 ns wide pulses using the second-harmonic from a Q-switched Nd:YAG laser, in air at atmospheric pressure. The plasma emission is detected with temporal resolution, using an Echelle spectrometer of wide spectral range (300-900 nm) combined with an intensified charge coupled device camera. A plasma temperature of 7800 400 K is determined using the Boltzmann plot method, from spectra obtained under optimized experimental conditions. As an example of an industrial application the concentration of copper in scrap metals is studied, which is an important factor to determine the quality of the samples to recycle. Cu concentrations down to 200 ppm can be detected. Another application of the laser-induced plasma spectroscopy method is the measurement of the nickel and copper concentrations in an iron-containing sample of reduced magma from the 1870s expedition to western Greenland by Adolf Erik Nordenskiold. Different spectral lines of nickel are used for calibration, and their results are compared.
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| 47. |
- Wagner, Annemarie, 1954, et al.
(författare)
-
Biomonitoring of trace elements in Vietnamese freshwater mussels
- 2004
-
Ingår i: Spectrochimica Acta Part B-Atomic Spectroscopy. - : Elsevier BV. - 0584-8547. ; 59:8, s. 1125-1132
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of the present study was to conduct a preliminary investigation of the pollution situation in the northern part of Vietnam with focus on trace elements including heavy metals. A freshwater bivalve species of the Unionidae family (Pletholophus swinhoei), abundant in this part of the country and frequently used for human consumption, was chosen as biomonitor. Ten specimens each were collected at two rural sites, Day Minh, approximately 40 km south of the capital Hanoi, and An Thin, situated approximately 11 km south of the Pha Lai power plant. The concentrations of 20 elements were measured using total reflection X-ray fluorescence and graphite furnace atomic absorption spectroscopy. Significant site-specific differences were found for the elements As, Ba, Be, Br, Cr, Fe, Mn, Ni, P and Sr. A comparison with other in situ biomonitoring studies using Unionidae bivalves showed that the concentrations of most elements were within the same order of magnitude, whereas heavy metal concentrations were distinctively low, suggesting the absence of major anthropogenic pollution sources in this area. The concentrations of Cd, Cr, Cu, Pb, Se and Zn were below the levels regarded as harmful according to the international standards for metals in mollusks compiled by the Food and Agricultural Organization of the United Nations. (C) 2004 Elsevier B.V. All rights reserved.
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| 48. |
- Wagner, Annemarie, 1954, et al.
(författare)
-
Total-Reflection X-ray fluorescence analysis of elements in size-fractionated particulate matter sampled on polycarbonate filters - Composition and sources of aerosol particles in Goteborg, Sweden
- 2010
-
Ingår i: Spectrochimica Acta - Part B: Atomic Spectroscopy. - : Elsevier BV. - 0584-8547. ; 65:6, s. 471-477
-
Konferensbidrag (refereegranskat)abstract
- This is the first study applying the technique of cold plasma ashing on polycarbonate filters as a preparative step for subsequent elemental analysis of aerosol particles by Total-Reflection X-ray fluorescence. The procedure has been validated by analyzing blanks of the filter material, chemicals used as additives as well as certified standard reference material. The results showed that cold plasma ashing is superior to conventional digestion methods with regard to the ease of sample preparation and contamination. A PIXE cascade impactor was used to collect size-fractionated aerosol particles in 9 size classes ranging from 16 to 0.06 mu m aerodynamic diameter at an urban and a suburban site in Goteborg, Sweden. Filter segments loaded with the aerosol particles were cut out and fixed on Quartz carriers. After adding 10 ng of Ga as internal standard the samples were dried, digested by cold plasma ashing and analyzed by Total-Reflection X-ray fluorescence. The analysis of aerosol particles showed that elemental concentrations at both the urban and the suburban site in Goteborg were low compared to central Europe. More and concurrent sampling of size-fractionated particles is required to identify local sources of trace elements in the urban area of Goteborg. (C) 2010 Elsevier B.V. All rights reserved.
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