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61.
62.
63.
The indirect ortho and para carbon-carbon coupling constants in benzene were determined utilizing the deuterium isotope effect on the carbon chemical shifts in 1-d1- and 1,3,5-d3-benzene. The measurements gave for J(CC, ortho) and J(CC, para) the values of 55.3 ± 0.5 Hz and 10.08 ± 0.10 Hz, respectively. The ratios of the direct dipolar C? C coupling constants were calculated using the previous results of 1-13C-benzene in an oriented phase. These ratios differ from the theoretical ones obtained assuming the benzene ring to be hexagonal, showing significant indirect contributions in the D values. 相似文献
64.
By recording two spectra of the same molecule in different nematic liquid crystals, and analysing the data simultaneously, information has been obtained on the molecular structures of 1,2,4,5- (1) and 1,2,3,4-tetrachlorobenzene (2). Carbon–hydrogen and carbon–carbon internuclear distance ratios, as well as bond lengths and bond angles, were computed and corrected for harmonic vibrations. Only part of the molecular structure of 2 could be derived with reasonable precision; the reasons for this limitation are discussed. The spectra of the two isomers were also analysed in isotropic solvents in order to determine the indirect coupling constants. One- and two-bond 13C isotope effects on the chemical shifts of the protons were observed. The solvent effects of the different nematic liquid crystals on the structure were found to be small compared with the experimental error. 相似文献
65.
W. Diehl 《Fresenius' Journal of Analytical Chemistry》1966,222(2):178-189
Zusammenfassung Röntgenfluorescenzeichkurven für die Schichtdicke dünner Edelmetallschichten werden berechnet. Die Annahme einer von der Schichtdicke unabhängigen konstanten Primärwellenlänge führt zum gleichen Kurventyp wie die Annahme eines polychromatischen Primärspektrums. Daraus wird geschlossen, daß für Elemente hoher Ordnungszahl das von einer Mo-Röhre emittierte Röntgenspektrum durch eine einzige Primärwellenlänge
p
ersetzt werden kann, welche unabhängig von der Schicht-dicke ist. Berechnungsmethoden und Werte für
p
werden angegeben.
Summary X-ray fluorescence calibration curves are calculated for film thicknesses of noble metals. The assumption of a constant primary wave-length independent of the film thickness gives the same type of curve as the assumption of a polychromatic primary spectrum. Therefore, it is concluded that—as far as metals with high atomic number are concerned—the spectrum emitted by a molybdenum X-ray tube may be replaced by a single wave-length p which does not depend on the film thickness. Calculation methods and values of p are given.相似文献
66.
M. Diehl Th Feldmann R. Jakob P. Kroll 《The European Physical Journal C - Particles and Fields》2005,39(1):1-39
We present a simple empirical parameterization of the x- and t-dependence of generalized parton distributions at zero skewness, using forward parton distributions as input. A fit to experimental data for the Dirac, Pauli and axial form factors of the nucleon allows us to discuss quantitatively the interplay between longitudinal and transverse partonic degrees of freedom in the nucleon (nucleon tomography). In particular we obtain the transverse distribution of valence quarks at given momentum fraction x. We calculate various moments of the distributions, including the form factors that appear in the handbag approximation to wide-angle Compton scattering. This allows us to estimate the minimal momentum transfer required for reliable predictions in that approach to be around
. We also evaluate the valence contributions to the energy-momentum form factors entering Jis sum rule.Received: 16 September 2004, Revised: 15 October 2004, Published online: 17 December 2004 相似文献
67.
Ledieu J Hoeft JT Reid DE Smerdon JA Diehl RD Lograsso TA Ross AR McGrath R 《Physical review letters》2004,92(13):135507
An ultrathin film with a periodic interlayer spacing was grown by the deposition of Cu atoms on the fivefold surface of the icosahedral Al70Pd21Mn9 quasicrystal. For coverages from 5 to 25 monolayers, a distinctive quasiperiodic low-energy electron diffraction pattern is observed. Scanning tunneling microscopy images show that the in-plane structure comprises rows having separations of S=4.5+/-0.2 A and L=7.3+/-0.3 A, whose ratio equals tau=1.618... within experimental error. The sequences of such row separations form segments of terms of the Fibonacci sequence, indicative of the formation of a pseudomorphic Cu film. 相似文献
68.
Volckova E Evanics F Yang WW Bose RN 《Chemical communications (Cambridge, England)》2003,(10):1128-1129
The helix-turn-helix motifs of the DNA binding domains of human polymerase-alpha and polymerase-kappa are dramatically perturbed upon binding to cisplatin with concomitant release of zinc. 相似文献
69.
M. Diehl P. Kroll C. Vogt 《The European Physical Journal C - Particles and Fields》2003,26(4):567-577
We study the handbag contribution to two-photon annihilation into baryon-antibaryon pairs at large energy and momentum transfer.
We derive factorization of the process amplitude into a hard subprocess and form factors describing the soft transition, assuming that the process is dominated by configurations where the (anti)quark approximately carries the full
momentum of the (anti)baryon. The form factors represent moments of time-like generalized parton distributions, so-called
distribution amplitudes. A characteristic feature of the handbag mechanism is the absence of isospin-two components in the
final state, which in combination with flavor symmetry provides relations among the form factors for the members of the lowest-lying
baryon octet. Assuming dominance of the handbag contribution, we can describe current experimental data with form factors
of plausible size, and predict the cross sections of presently unmeasured channels.
Received: 3 July 2002 / Revised version: 7 October 2002 / Published online: 20 November 2002
RID="a"
ID="a" e-mail: mdiehl@physik.rwth-aachen.de
RID="b"
ID="b" e-mail: kroll@physik.uni-wuppertal.de
RID="c"
ID="c" e-mail: cvogt@nordita.dk 相似文献
70.
Luk KB Diehl HT Duryea J Guglielmo G Heller K Ho PM James C Johns K Longo MJ Rameika R Teige S Thomson GB Zou Y 《Physical review letters》2000,85(23):4860-4863
A search for direct CP violation in the nonleptonic decays of hyperons has been performed. In comparing the product of the decay parameters, alpha(Xi)alpha(Lambda), in terms of an asymmetry parameter, A(XiLambda), between hyperons and antihyperons in the charged Xi-->Lambdapi and Lambda-->ppi decay sequence, we found no evidence of direct CP violation. The parameter A(XiLambda) was measured to be 0.012+/-0.014. 相似文献