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41.
Thermal and photochemically induced intramolecular 1,3-dipolar cycloaddition reactions of 4-phenyl-3-(2-allylphenyl)-sydnone The title compound 9 was synthesised in the usual way, starting from 2-allylaniline and ethyl 2-bromo-2-phenylacetate, via the nitrosaminacid 8 (Scheme 2). 9 reacts at room temperature with its potential azomethinimine-function in an intramolecular [3+2]-cycloaddition to give the tricyclic compound 11 (Scheme 2). On irradiation, 9 yields the dihydro-3H-pyrazolo[2,3-a]indole 10 which probably arises by intramolecular [3+2]-cycloaddition of the corresponding intermediate nitrilimine. 相似文献
42.
F. N. Gygax E. Lippelt A. Schenck A. J. van der Wal S. Barth 《Hyperfine Interactions》1986,31(1-4):447-453
In continuation of our earlier studies of the anomalous temperature dependence of the μ+ Knight shift Kμ in Cd,CdHg (1.2 at %) andCdMg (3.38 at %) — interpreted as due to Van Hove-type singularities in the local density of electron states /1/ — we have studied
the temperature dependence of the μ+ Knight shift in polycrystallineCdMg (1.04 at %, 2.05 at %) and in a single crystal ofCdMg (2.5 at %). In contrast to pure Cd no anisotropies in Kμ could be detected. The temperature dependence of Kμ in aCdMg (2.05 at %) sample and in the monocrystallineCdMg (2.5 at %) sample essentially reproduces the one previously observed in polycrystallineCdMg (3.38 at %), showing a steplike discontinuity and a logarithmic singularity. A complete different behaviour is observed
inCdMg (1.04 at %), where no logarithmic singularity seems to show up and where a steplike discontinuity of opposite sign at around
90 K is clearly seen. If these singularities are still to be interpreted in terms of Van Hove singularities, the question
arises why there is such a nonlinear dependence on the Mg concentration. 相似文献
43.
M. Weber P. Birrer F. N. Gygax B. Hitti E. Lippelt H. Maletta A. Schenck 《Hyperfine Interactions》1991,63(1-4):93-101
The muon spin relaxation was measured in the high-T
c superconductors Bi2Sr1.3Ca0.7 CuO6.15, Bi2Sr2CaCu2O8 and Bi2Pb
x
Sr2Ca2Cu3O10. We present our method to determine the London penetration depth perpendicular toc-axis λ⊥ (0) taking also contributions from the anisotropic magnetization and nuclear dipoles to the muon frequency spectrum into
account. 相似文献
44.
de Visser A Graf MJ Estrela P Amato A Baines C Andreica D Gygax FN Schenck A 《Physical review letters》2000,85(14):3005-3008
Transverse-field muon spin relaxation measurements have been carried out on the heavy-fermion superconductor UPt (3) doped with small amounts of Pd. We find that the critical Pd concentration for the emergence of the large-moment antiferromagnetic phase is approximately 0.6 at. %Pd. At the same Pd content, superconductivity is completely suppressed. The existence of a magnetic quantum critical point in the phase diagram, which coincides with the critical point for superconductivity, provides evidence for ferromagnetic spin-fluctuation mediated odd-parity superconductivity, which competes with antiferromagnetic order. 相似文献
45.
46.
47.
The electrodeposition of Sb and Bi on gold electrodes from HCl solutions was studied using a voltammetric thin layer technique. The metal deposition is preceded by the formation of cation adsorption monolayers. Alloy formation could not be observed. 相似文献
48.
The Fermi contact hyperfine contribution to the Knight shift of positive muons, implanted at the interstitial 3d sites in CeB6, is found to exhibit the same temperature dependence below T(Q) in phase II as the quadrupolar order parameter determined from resonant and nonresonant x-ray scattering. Furthermore, the contact coupling parameter is shown to be anisotropic and field dependent. These unanticipated features are interpreted to arise from the RKKY induced conduction electron spin polarization, which depends on the orientation and expectation value of the ordered 4f quadrupole moments. 相似文献
49.
A. Schenck P. Birrer F. N. Gygax B. Hitti E. Lippelt H. Maletta M. Weber 《Hyperfine Interactions》1991,63(1-4):227-233
Transverse field studies (0.3 T) in HoBa2Cu3O7, DyBa2Cu3O7 and ErBa2Cu3O7 (x=6.40. 6.45, 6.53, 7) were undertaken with the aim of detecting a possible 4f-moment inducedμ
+ Knight shift which could elucidate the nature of the magnetic coupling among the 4f-moments and a possible interference with
superconductivity. AboveT
c
no shift could be detected in any of the systems except in HoBa2Cu3O7 where a split signal appears involving a positive and a negative shift. Unexpected shifts may be present belowT
c
. 相似文献
50.
The photoelectron spectra of the four oxygen and nitrogen analogs of thiathiophthene 1 to 4 are reported and discussed. The first two bands are assigned to ionization from the π- and n-molecular orbitals on the basis of CNDO/2 calculations. The assignment of bands and to ionization from π-molecular orbitals is suggested. 相似文献