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131.
D. Herlach G. Majer J. Major J. Rosenkranz M. Schmolz W. Schwarz A. Seeger W. Templ E. H. Brandt U. Essmann K. Fürderer M. Gladisch 《Hyperfine Interactions》1991,63(1-4):41-48
The spin precession of positive muons in ultra-pure Nb single crystals of high perfection, cooled down in transverse magnetic
fields 0.68B
c2≤B
appl≤0.84B
c2 (B
c2=upper critical field) from temperatures well above the superconducting transition temperatureT
c=9.25 K, has been investigated in the temperature range 2.6 K≤T≤8.0 K. The experiments confirm the periodic fieldB(r) of triangular flux-line lattices as calculated from numerical solutions of the microscopic BCS-Gor'kov theory. The observed
broadening of the van Hove singularities in the field distribution is discussed in terms of the combined effects of muon diffusion
and random perturbations of the flux-line lattice. 相似文献
132.
CD data of the optically active 4-hydroxy (1–5) and 4-acetoxy chromans (6–8) were analyzed by two different approaches. The Snatzke-Antus treatment of chiraly perturbed chromane chromophore revealed M absolute conformation and 4S absolute configuration of the alcohols, i.e. P absolute conformation and 4R absolute configuration of the acetates. The proposed absolute configuration of the optically active alcohols was confirmed for 1 and 2 by the chiral excitone coupling method applied on their benzoates 9 and 10. 相似文献
133.
Stefan Minniberger Fritz Diorico Stefan Haslinger Christoph Hufnagel Christian Novotny Nils Lippok Johannes Majer Christian Koller Stephan Schneider Jörg Schmiedmayer 《Applied physics. B, Lasers and optics》2014,116(4):1017-1021
We report the realization of a robust magnetic transport scheme to bring >3 × 108 ultracold 87Rb atoms into a cryostat. The sequence starts with standard laser cooling and trapping of 87Rb atoms, transporting first horizontally and then vertically through the radiation shields into a cryostat by a series of normal- and superconducting magnetic coils. Loading the atoms in a superconducting microtrap paves the way for studying the interaction of ultracold atoms with superconducting surfaces and quantum devices requiring cryogenic temperatures. 相似文献
134.
Katharina Majer Prof. Ruth Signorell Dr. Maarten F. Heringa Maximilian Goldmann Dr. Patrick Hemberger Dr. Andras Bodi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(62):14192-14204
The photoionization of thymine has been studied by using vacuum ultraviolet radiation and imaging photoelectron photoion coincidence spectroscopy after aerosol flash vaporization and bulk evaporation. The two evaporation techniques have been evaluated by comparison of the photoelectron spectra and breakdown diagrams. The adiabatic ionization energies for the first four electronic states were determined to be 8.922±0.008, 9.851±0.008, 10.30±0.02, and 10.82±0.01 eV. Vibrational features have been assigned for the first three electronic states with the help of Franck–Condon factor calculations based on density functional theory and wave function theory vibrational analysis within the harmonic approximation. The breakdown diagram of thymine, as supported by composite method ab initio calculations, suggests that the main fragment ions are formed in sequential HNCO-, CO-, and H-loss dissociation steps from the thymine parent ion, with the first step corresponding to a retro-Diels–Alder reaction. The dissociation rate constants were extracted from the photoion time-of-flight distributions and used together with the breakdown curves to construct a statistical model to determine 0 K appearance energies of 11.15±0.16 and 11.95±0.09 eV for the m/z 83 and 55 fragment ions, respectively. These results have allowed us to revise previously proposed fragmentation mechanisms and to propose a model for the final, nonstatistical H-loss step in the breakdown diagram, yielding the m/z 54 fragment ion at an appearance energy of 13.24 eV. 相似文献
135.
L.E. Valiente-Banuet G. Majer K. Müller 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,200(2):280-284
Advanced nuclear magnetic resonance (NMR) techniques were applied to study the local environments of hydrogen in NaAlH4. Through a combined application of the magic echo (ME) and the magic Hahn echo (MHE) sequences the hetero- and homonuclear contributions to the dipolar second moment (M2) were determined separately. The obtained values are compared with the second moments calculated by the van Vleck formulae, using structural data determined by neutron scattering on NaAlD4. This comparison indicates structural differences between NaAlH4 and NaAlD4. A model is suggested for the orientation of the [AlH4]− tetrahedra in NaAlH4, for which the calculated second moments are in good agreement with the experimentally observed values. 相似文献
136.
137.
138.
Positive mouns in iron: Dipolar fields at tetrahedral sites and jump frequencies at low temperatures
M. Schmolz K. -P. Döring K. Fürderer M. Gladisch N. Haas D. Herlach G. Majer J. Rosenkranz W. Schäfer L. Schimmele W. Schwarz A. Seeger E. Yagi 《Hyperfine Interactions》1986,31(1-4):199-204
On polycrystalline and monocrystalline iron muon-spin precession frequencies and transverse relaxation rates have been measured
down to 0.5 K. In the polycrystalline sample two distinct precession frequencies were observed at and below 1.4 K. They are
attributed to the different dipolar fields at magnetically inequivalent tetrahedral interstices seen by muons moving locally
around impurities. By contrast, in monocrystalline iron we observed only one precession frequency in monocrystalline iron
with a damping rate which increased with decreasing temperature down to 0.5 K. We attribute the difference between the monocrystalline
and the polycrystalline sample to different impurity contents. The single-crystal data are discussed in terms of μ+ diffusion by hopping between interstitial sites of tetragonal symmetry. The answer to several open questions is expected
from an extension of the measurements to lower temperatures. 相似文献
139.
140.
We show that the cardinality of a nonempty set of points without tangents in the desarguesian projective plane PG(2, q), q even, is at least q + 1 + $ \sqrt {q/6} $ provided that the set is not of even type. 相似文献