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51.
52.
Abstract A novel microcombustion technique for carbon isotopic analysis of nanogram amounts of carbon in non-volatile materials based on isotope ratio monitoring (irm) mass spectrometry is described. Liquid or solid samples placed in a quartz sleeve are combusted at 1000°C in a continuous stream of helium and oxygen. CO(2) removed from the carrier gas stream by cryogenic trapping is transferred onto a GC column. Following GC separation, the CO(2) is transferred via an open split to the ion source of a gas isotope ratio mass spectrometer. Reproducibility for samples >25 nmol carbon is <1‰. Problems associated with blanks from various sources and with reproducible deposition of small sample amounts led to variable accuracy, which was dependent on the compound class being analysed. Minimum sample size was in the range from 5 to 10 nmol carbon. Measurements of dissolved organic carbon (DOC) of groundwater from Germany yielded consistent values of δ(13)C = -28.8‰. 相似文献
53.
M. Veselský Š. Šáro F. P. Heßberger V. Ninov S. Hofmann D. Ackermann 《Zeitschrift für Physik A Hadrons and Nuclei》1996,356(1):403-410
Velocity distributions and production cross sections of evaporation residues have been measured in the reaction20Ne+208Pb at projectile energies of 8.6, 11.4, 14.9 A.MeV. Essential deviations from statistical model of deexcitation have been
observed. Monte Carlo simulations involving emission of non-equilibrium particles have been used in order to reproduce experimental
velocity, charge and mass distributions of evaporation residues and to estimate indirectly multiplicities of pre-equilibrium
particles.
Communicated by V. Metag 相似文献
54.
M. Leino J. Uusitalo R. G. Allatt P. Armbruster T. Enqvist K. Eskola S. Hofmann S. Hurskanen A. Jokinen V. Ninov R. D. Page W. H. Trzaska 《Zeitschrift für Physik A Hadrons and Nuclei》1996,355(1):157-164
Neutron-deficient isotopes of radium have been produced in the reactions35Cl+175Lu,40Ar+170,171Yb, and36Ar+170,171Yb and separated in-flight with a gas-filled recoil separator. The activities have been identified on the basis of correlated alpha decay chains. The alpha particle energy Eα and the half-life T1/2 of an isomeric state of the new isotope,203m Ra, have been determined to be (7615±20) keV and (33 ?10 +22 ) ms, respectively. An assignment of another decay with Eα = (7577±20) keV and T1/2=(1.1 ?0.5 +5.0 ) ms to203g Ra is made on the basis of one observed three-decay chain. Tentative evidence for the production of the new isotope202Ra is also given. The values Eα = (7860±60) keV and T1/2=(0.7 ?0.3 +3.3 ) ms were measured. Improved decay data have been obtained for204Ra. The results are Eα = (7484±10) keV and T1/2=(59 ?9 +12 ) ms. Earlier findings concerning the decay of two states in205Ra and an isomer in207Ra have been confirmed. Approximate values for cross sections have been determined for202Ra, produced using the36Ar+170Yb reaction and for203Ra,204Ra, and205Ra using the35Cl+175Lu reaction. The results are 2 nb (202Ra), 4 nb (203Ra), 40 nb (204Ra), and 800 nb (205Ra). 相似文献
55.
One-parameter semigroups occurring in operator-limit distributions are investigated. The topological-algebraic background of the relevant monoids is discussed and Lie semigroup theory is applied to the Urbanik Decomposability Semigroup. 相似文献
56.
We consider, both for unpolarized and longitudinally polarized electron beams, the reaction $e^ + e^ - \to t\bar t$ with subsequent semileptonict and nonleptonic $\bar t$ decay and vice versa and investigate optimized angular correlations which are sensitive to CP non-conservation in the $t\bar t$ production vertex. We calculate these correlations for two-Higgs-doublet extensions and the minimal super-symmetric extension of the Standard Model (SM) with CP violation beyond the Kobayashi-Maskawa phase. While the sensitivity of the optimal correlation for tracing dispersive CP effects is enhanced with longitudinally polarized electron beams, we find that the sensitivity of the best correlation for probing absorptive CP effects is almost independent of the polarization degree. 相似文献
57.
P. Ackerbauer W. H. Breunlich M. Fuchs S. Fussy M. Jeitler P. Kammel B. Lauss J. Marton W. Prymas J. Werner J. Zmeskal K. Lou C. Petitjean P. Baumann H. Daniel F. J. Hartmann W. Schott T. von Egidy P. Wojciechowski D. Chatellard J. P. Egger E. Jeannet T. Case K. M. Crowe R. H. Sherman V. Markushin 《Hyperfine Interactions》1993,82(1-4):243-258
Complementary to the investigations of the most efficient dt cycle, also the other muon-induced fusion cycles in mixtures of hydrogen isotopes have been studied. The results of these dedicated experiments provide rich information about muon-induced few-body reactions and contribute significantly to a better overall understanding of CF. A summary of the recent progress will be presented. Special emphasis will be put on two characteristic examples, namely a new experimental approach to study the muonic cascade in H-D mixtures and the systematic study of hyperfine effects in muon-induced reactions. 相似文献
58.
P. Ackerbauer J. Werner W. H. Breunlich M. Cargnelli M. Jeitler P. Kammel J. Marton N. Nägele A. Scrinzi J. Zmeskal J. Bistirlich K. M. Crowe C. Petitjean R. H. Sherman P. Baumann H. Bossy H. Daniel F. J. Hartmann W. Schott T. von Egidy W. Neumann 《Hyperfine Interactions》1993,82(1-4):357-372
A main source of information about the muon-catalyzed fusion cycle in D-T mixtures are the cycling rates c, which are characteristic for the kinetic equilibrium of states attained rapidly in dense targets. The measurement, analysis and interpretation of these rates will be discussed, concentrating on the extensive set of rates observed at PSI over the last decade in gaseous, liquid and solid targets.Invited talk presented by Peter Kammel. 相似文献
59.
Based on thermodynamic analysis of interfacial segregation, the segregation enthalpy H
o of a solute I in a given matrix was found to depend linearly on two mutually independent terms reflecting the type of interface and the solid solubility limit X
infI
sup*
at temperature T and can be written as In this equation, the structural dependence of interfacial segregation is contained in H
*() which corresponds to the extrapolated segregation enthalpy of a solute with unlimited solubility in the matrix. The product [Tln(X
infI
sup*
)] is essentially constant with temperature, and can therefore be obtained from data for maximum solid solubility, [Tln(X
infI
sup*
)]max. The parameter v>0 represents the relationship between the activity a
infI
sup*
of a solute at the bulk solid solubility limit in a given matrix and X
infI
sup*
, a
infI
sup*
=(X
infI
sup*
)
v
, and is characteristic for the matrix. Using recent experimental data for silicon, phosphorus, and carbon segregation at well-characterized grain boundaries in oriented bicrystals of -iron, the averaged value
was determined. Values of H
*() range from -8 kJ/mol (general grain boundaries) up to +8 kJ/mol (special grain boundaries). These values are discussed and used for a more precise and generalized construction of grain boundary segregation diagrams of -iron. 相似文献
60.