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91.
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94.
S. Raeder N. Stöbener T. Gottwald G. Passler T. Reich N. Trautmann K. Wendt 《Spectrochimica Acta Part B: Atomic Spectroscopy》2011,66(3-4):242-247
The long-lived radio isotope 237Np is generated within the nuclear fuel cycle and represents a major hazard in the final disposal of nuclear waste. Related geochemical research requires sensitive methods for the detection of ultratrace amounts of neptunium in environmental samples. Resonance ionization mass spectrometry (RIMS) has proven to be one of the most sensitive methods for the detection of plutonium. A precondition for the application of RIMS to ultratrace analysis of neptunium is the knowledge of an efficient and selective scheme for optical excitation and ionization. Therefore, a multitude of medium to high-lying atomic levels in neptunium was located by applying in-source resonance ionization spectroscopy. By using excitation via six previously known first excited, intermediate levels of odd parity, a set of twelve so far unknown high-lying levels of even parity were identified and studied further for their suitability in resonant excitation/ionization schemes. Autoionizing resonances for efficient ionization of neptunium atoms were subsequently accessed spectroscopically. Altogether five resonance ionization schemes were investigated and characterized concerning their saturation behavior and relative efficiency. Applying a calibrated sample, an overall efficiency of 0.3% was determined. 相似文献
95.
Xiaolong Li Yueming Wang Thomas Allgurén Klas Andersson Jost O.L. Wendt 《Proceedings of the Combustion Institute》2021,38(3):4309-4316
The focus of this paper is on effects of chlorine and sulfur on coal ash deposition rates, under practically relevant but systematically controlled combustion conditions. This problem is important, not so much for coal, but to understand and predict deposition rates for biomass combustion where chlorine contents can be high. To this end, ash deposition rates on a controlled temperature surface were measured for controlled amounts of chlorine and sulfur added to a pulverized coal, doped with potassium and burned in a 100 kW rated combustion rig. Previous work with 35 tests on 11 coal, biomass and petroleum coke fuels burned under a range of operating conditions had strongly suggested that the deposition rate of the tightly bound inside deposits was independent of the ash aerosol composition, and depended only on PM1 in the flue gas. The loosely bound outside deposition rate was dependent primarily on the total alkali content in the flue gas. The new results using chlorine added to the fuel (in the form of ammonium chloride) required these previous conclusions to be drastically revised. They showed that chlorine, not alkali alone, had large effects on the deposition rate of the inside deposits, which now were orders of magnitude higher than without chlorine addition, and did not fit previous (multi-fuel) correlations with PM1. Sulfur addition, together with chlorine, did not affect deposition rates much, although it did lower the chlorine content of the deposit. These results are interpreted in terms of the ash aerosol size segregated composition, which was also measured, and potential sulfation reactions within the deposit. 相似文献
96.
A study on the systematic of the atomic ionization potentials for both, the lanthanide and actinide elements have been performed. The existing experimental basis, predominantly relying on results from resonance ionization spectroscopy, has been extended by novel laser spectroscopic investigations on the elements Au, Dy, Pr and Pa. Conclusive results of suitable precision for the ionization potentials could be obtained except for Pa, due to the complexity of its atomic spectrum. Nevertheless, a consistent interpretation of the observed trends for the ionization potentials of lanthanides and actinides was attempted. The series of lanthanides depicts the two well-known, completely smooth, linear trends above and below half-shell closure, from which an expectation value for the missing ionization potential of the all radioactive element promethium of IP Pm= 44985(140) cm ?1 was derived. In contrast, the lighter members of the actinide series below the half-filled shell exhibit a significant deviation from predictions, which are ascribed dominantly to relativistic influences affecting the energetic position of the multitude of low-lying configurations. With the assumption of removal of a 6d electron during the ionization process agreement between theory and experiment and a smooth, even though not linear behavior, is obtained also in this region of the Periodic Table. This new interpretation could help to better predict similar trends and systematics for elements heavier than the actinides. Particularly relevant in this respect are the super-heavy elements, which are produced only in minuscule atom numbers and thus were not accessible for any atomic physics study yet. 相似文献
97.
Benefiting from the continuous laser developments, resonance ionization can be applied for a variety of experiments on radioactive
isotopes, e.g. as a laser ion source for producing pure beams of short-lived isotopes at on-line facilities. In this paper
the application of a compact set-up for resonance ionization mass spectrometry for ultra-trace analysis of the long-lived
isotope Ca-41 is described. With this set-up a purely optical selectivity of 3×109 and an overall detection efficiency of 1.2(4)×10−5 are demonstrated. 相似文献
98.
K. Wendt K. Blaum B. A. Bushaw C. Grüning R. Horn G. Huber J. V. Kratz P. Kunz P. Müller W. Nörtershäuser M. Nunnemann G. Passler A. Schmitt N. Trautmann A. Waldek 《Analytical and bioanalytical chemistry》1999,364(5):471-477
Resonance Ionization Mass Spectrometry (RIMS) has nowadays reached the status of a routine method for sensitive and selective
ultratrace determination of long-lived radioactive isotopes in environmental, biomedical and technical samples. It provides
high isobaric suppression, high to ultra-high isotopic selectivity and good overall efficiency. Experimental detection limits
are as low as 106 atoms per sample and permit the fast and sensitive determination of ultratrace amounts of radiotoxic contaminations. Experimental
arrangements for the detection of different radiotoxic isotopes, e.g. 236–244Pu, 89,90Sr and 99Tc in environmental samples are described, and the application of RIMS to the ultrarare long-lived radioisotope 41Ca for cosmochemical, radiodating and medical purposes are presented.
Received: 17 December 1998 / Revised: 11 February 1999/Accepted: 18 February 1999 相似文献
99.
Hideki Tomita Christoph Mattolat Sebastian Raeder Seiji Sasada Yuki Higuchi Kunisuke Takezawa Takayoshi Muramatsu Tetsuo Iguchi Klaus Wendt 《Hyperfine Interactions》2010,196(1-3):169-176
Stable isotope analysis using Laser Ablation Assisted Resonant Ionization Mass Spectrometry (LA-RIMS) is discussed. For the case of the 87Sr/86Sr isotope ratio measurements with a single color two-photon excitation scheme, the mass discrimination effects, which occur in LA-RIMS, are analyzed and a precision of 0.6% was extracted. For preparation of LA-RIMS on Hf isotopes, a novel two-color resonant excitation scheme with subsequent non-resonant ionization has been established using a high repetition-rate Ti:Sapphire laser system. 相似文献
100.
K. Zimmer J. Stenner H. -J. Kluge J. Lantzsch L. Monz E. W. Otten G. Passler R. Schwalbach M. Schwarz H. Stevens K. Wendt G. Herrmann S. Nieß N. Trautmann K. Walter B. A. Bushaw 《Applied physics. B, Lasers and optics》1994,59(2):117-121
A new, fast technique for trace analysis of the radioactive isotopes89Sr and90Sr in environmental samples has been developed. Conventional mass separation is combined with resonance ionization spectroscopy in collinear geometry, which provides high selectivity and sensitivity. In addition, a chemical separation procedure for sample preparation has been developed. The described technique was used to determine the90Sr content in 870 m3 air samples collected near Munich during and shortly after the Chernobyl reactor accident in April 1986. The content of90Sr was measured to be 1.4 mBq per m3, corresponding to 1.6 × 109 atoms of90Sr per sample. This value is in good agreement with the results of radiochemical measurements.This publication comprises part of the Dissertations of J. Stenner and K. Zimmer 相似文献