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41.
JD Debord S Della-Negra FA Fernandez-Lima SV Verkhoturov EA Schweikert 《The journal of physical chemistry. C, Nanomaterials and interfaces》2012,116(14):8138-8144
Carbon cluster emission from thin carbon foils (5-40 nm) impacted by individual Au(n) (+q) cluster projectiles (95-125 qkeV, n/q = 3-200) reveals features regarding the energy deposition, projectile range, and projectile fate in matter as a function of the projectile characteristics. For the first time, the secondary ion emission from thin foils has been monitored simultaneously in both forward and backward emission directions. The projectile range and depth of emission were examined as a function of projectile size, energy, and target thickness. A key finding is that the massive cluster impact develops very differently from that of a small polyatomic projectile. The range of the 125 qkeV Au(100q) (+q) (q ≈ 4) projectile is estimated to be 20 nm (well beyond the range of an equal velocity Au(+)) and projectile disintegration occurs at the exit of even a 5 nm thick foil. 相似文献
42.
43.
S. M. Kormali E. A. Schweikert 《Journal of Radioanalytical and Nuclear Chemistry》1986,100(1):197-201
The reaction103Rh(p, n)103Pd was investigated for the trace detection of Rh. Maximum activation of Rh with minimal interferences was achieved with protons of 11 MeV. The detection limit for the nondestructive assay of Rh is 0.03 ppm. 相似文献
44.
J. R. McGinley G. J. Stock E. A. Schweikert J. B. Cross R. Zeisler L. Zikovsky 《Journal of Radioanalytical and Nuclear Chemistry》1978,43(2):559-573
Heavy ion activation has been studied as a method for determining hydrogen. The reactions used [e.g.1H(7Li, n)7Be] are the “inverse” of well known reactions [e.g.7Li(p, n)7Be]. Nuclear activation parameters for the ion beams of interest (7Li2+,10B2+) have been studied. The analytical feasibility is demonstrated with the determination of hydrogen in titanium at the 100
and 30 ppm levels with relative precisions of 8 to 10%. Detection limits in titanium are in the 0.1 to 0.5 ppm range. Heavy
ion bombardment is also accompanied by the emission of characteristic X-rays (“atomic” activation). The parameters governing
X-ray emission and background production have been investigated. Experimental K and L X-ray yields from thick targets have
been measured for many elements excited by On+ beams of 0.5 to 7 MeV/amu and Kr7+ beams of 0.5 to 1 MeV/amu. The simultaneous determination of trace elements at levels of 10 to several 100 ppm in microsamples
(∼10−5 g) is demonstrated on biological specimens. K and L X-ray yields and corresponding detection limits have also been measured
with the7Li2+ and10B2+ beams used for the nuclear activation of hydrogen. With these beams (∼6 MeV/amu) simultaneous nuclear and atomic activation
is possible, yielding an unusual multielement trace analysis capability covering hydrogen and medium and high Z elements. 相似文献
45.
J. R. Mcginley L. Žikovský E. A. Schweikert 《Journal of Radioanalytical and Nuclear Chemistry》1977,37(1):275-283
The use of heavy ion activation as a method for the analysis of hydrogen and deuterium has been evaluated. Thick target yields
from reactions of7Li,10B,11B and19F on1H and2H have been determined; activation curves for many of these reactions are presented and interferences are evaluated. Hydrogen
has been determined in titanium via1H(10B, α)7Be at the 100 and 33 ppm levels with relative precisions of 8 to 10%. 相似文献
46.
S. A. Dabney D. L. Swindle J. N. Beck G. Francis E. A. Schweikert 《Journal of Radioanalytical and Nuclear Chemistry》1973,16(2):375-383
An analytical method is described for the determination of trace amounts of sulfur by charged particle activation analysis.
The method consists of proton irradiation followed by a rapid radiochemical separation of the product nuclide,34m Cl. This procedure has been applied to a number of pure metal samples which range in sulfur content from 0.3 to 30 ppm. All
analyses were repeated several times to ensure consistent results and to better evaluate experimental detection limits and
systematic errors. The results indicate that sulfur determinations can be performed at a concentration of less than 1.0 ppm.
Activation curves are presented for the reactions S(d,x)34mCl, S(p,x)34mCl, and the interfering reaction35Cl(p, pn)34mCl.
In memoriam. 相似文献
47.
The (3)He activation method for oxygen determination was applied to chalcogenide materials such as Ge(28)Sb(12)Se(60) and Ge(33)As(12)Se(55). Attention was focused on the optimization of the (3)He bombardment energy for non-destructive oxygen determination and the validity of the post-irradiation chemical etch used for removing surface oxygen contamination. The procedure developed was tested on a series of chalcogenide glasses. The detection limit for this non-destructive technique using ~6-MeV (3)He is estimated at ~1 ppm of oxygen. 相似文献
48.
L. Van Vaeck J. Bennett P. Van Epsen E. Schweikert R. Gijbels F. Adams W. Lauwers 《Journal of mass spectrometry : JMS》1989,24(9):782-796
Laser microprobe mass spectrometry (LMMS) has been used to systematically study polyfunctional molecules, covering a wide range of structure and polarity. The knowledge about the mechanisms actually involved for desorption and ionization (DI) of organics by laser microbeam irradiation of solid samples at high-power density is rather limited. Therefore we have elaborated a set of tentative hypotheses about DI in LMMS, permitting consistent rationalization of detected signals. The technique apparently combines desorption under mild conditions, shown by the release of intact thermolabiles, with extensive fragmentation. Structural data are typically distributed between cations and anions. Interpretation of negative-ion detection mode mass spectra often represents intricate problems, partly due to the lack of sustaining background information from conventional mass spectrometry. Selected examples are presented to illustrate the occurrence of electron capture ionization, the role of heteroatoms in the formation of negative ions and the tendency to undergo complex skeletal rearrangements. Although LMMS was originally aimed at microprobe applications, it has been found to be a valuable tool in organic mass spectrometry. 相似文献
49.
Trace analysis methods have been developed for determining thallium, lead and bismuth. Proton or deuteron activation is used
followed by a radiochemical separation of the reaction products:203Pb from thallium,206Bi from lead, and207Po from bismuth. Activation curves are presented for different nuclear reactions occuring on the elements studied. Determinations
have been carried out on high purity samples containing varying amounts of thallium, lead, and bismuth. Based on experimental
data, the detection limits are estimated at 0.01 ppm for lead, and 0.001 ppm for thallium and bismuth, respectively. 相似文献
50.
Loebbecke S. Schuppler H. Schweikert W. 《Journal of Thermal Analysis and Calorimetry》2003,72(2):453-463
3,6-Bis(2H-tetrazol-5-yl)-1,2,4,5-tetrazine BTT and 3,3'-azobis(6-amino-1,2,4,5-tetrazine) (DAAT) are nitrogen-rich substances
considered as new components for energetic applications like gas generators. Therefore, the thermal decomposition behaviour
of BTT and DAAT was thermoanalytically characterized. Both substances decompose at surprisingly high temperatures of >200°C.
The decomposition heats released belong to the highest ever measured for energetic materials under similar experimental conditions
and are spread over a relatively narrow temperature range. The online monitoring of the decomposition gases reveals the decomposition
pathway which is initiated by ring opening reactions of the tetrazole and tetrazine subunits. Subsequent reaction steps could
be identified leading to a residue-free degradation of the C-N-backbone of BTT and DAAT.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献