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31.
Emanuel Vogel Hans-Wilhelm Engels Saichi Matsumoto Johann Lex 《Tetrahedron letters》1982,23(17):1797-1800
An expedient new synthesis of benzo[c]octalene starting from the Diels-Alder adduct of benzocyclobutadiene to 7,8-dimethylenecycloocta-1,3,5-triene is described. This octalene derivative, in solution, exists as an equilibrating mixture of the double bond isomers (2) and (3) whereas in its crystalline state only the isomer (2) is present. 相似文献
32.
Ohne Zusammenfassung 相似文献
33.
C. Günther G. Strube U. Wehmann W. Engels H. Blumberg H. Luig R. M. Lieder E. Bodenstedt H. J. Körner 《Zeitschrift für Physik A Hadrons and Nuclei》1965,183(5):472-498
A differential measurement of the spin rotation of Dy160 in the 2+ rotational state was performed by using liquid sources of TbCl3 solved in 3M HCl and applying an external magnetic field of 33 500 Gauss. No change of the Larmor precession frequency could be detected within the first 10·10?9 s. It is concluded that the ground state of the electronic shell of Dy+++ is reached in 6·10?10 s after theβ-decay of Tb160. The valueg R=+0.364±0.011 was derived using 〈r?3〉eff=8.92 a. u. for the 4f-shell of Dy+++. A comparison with the result ofCohen who studied the Mössbauer-effect in Fe2Dy shows that the value of 〈r?3〉eff must be 10% larger in this compound. A measurement of the effective magnetic field at the position of the nucleus in a source of terbium metal was performed for different temperatures. It revealed a temperature dependence which is very similar to the paramagnetic susceptibility χ(T). We observed a strong attenuation ofγ γ-angular correlations in the 2+ rotational state. For liquid sources of TbCl3 solved in 3M HCl the following attenuation parameters were measured:
$$\begin{gathered} \lambda _2 = (0.122 \pm 0.013) \cdot 10^9 {\text{s}}^{ - {\text{1}}} , \hfill \\ \lambda _4 = (0.235 \pm 0.024) \cdot 10^9 {\text{s}}^{ - {\text{1}}} . \hfill \\ \end{gathered}$$ 相似文献
34.
Dr. Hermann Engels 《Numerische Mathematik》1972,19(3):230-237
Summary Starting with a general definition of numerical differentiation procedures a necessary and a sufficient condition for pointwise convergence of such differentiation procedures is given. These conditions are applied to some detailed differentiation procedures. 相似文献
35.
J. W. Bats J. Parsch J. W. Engels 《Acta Crystallographica. Section C, Structural Chemistry》1999,55(7):IUC9900069-IUC9900069
36.
G. Bollen F. Ames G. Audi D. Beck J. Dilling O. Engels S. Henry F. Herfurth A. Kellerbauer H.-J. Kluge A. Kohl E. Lamour D. Lunney R. B. Moore M. Oinonen C. Scheidenberger S. Schwarz G. Sikler J. Szerypo C. Weber 《Hyperfine Interactions》2001,132(1-4):213-220
Penning trap mass spectrometry has reached a state that allows its application to very short-lived nuclides available from
various sources of radioactive beams. Mass values with outstanding accuracy are achieved even far from stability. This paper
illustrates the state of the art by summarizing the status of the ISOLTRAP experiment at ISOLDE/CERN. Furthermore, results
of mass measurements on unstable rare earth isotopes will be given.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
37.
Christoph Stampfer Stefan Fringes Johannes Gfittinger Francoise Molitor Christian Yolk Bernat Terrds Jan Dauber Stephan Engels Stefan Schnez Arnhild Jacobsen Susanne Droscher Thomas Ihn Klaus Ensslin 《Frontiers of Physics》2011,6(3):271-293
Graphene nanostructures are promising candidates for future nanoelectronics and solid-state quantum information technology. In this review we provide an overview of a number of electron transport experiments on etched graphene nanostructures. We briefly revisit the electronic properties and the transport characteristics of bulk, i.e., two-dimensional graphene. The fabrication techniques for making graphene nanostructures such as nanoribbons, single electron transistors and quantum dots, mainly based on a dry etching ??paper-cutting?? technique are discussed in detail. The limitations of the current fabrication technology are discussed when we outline the quantum transport properties of the nanostructured devices. In particular we focus here on transport through graphene nanoribbons and constrictions, single electron transistors as well as on graphene quantum dots including double quantum dots. These quasi-one-dimensional (nanoribbons) and quasi-zero-dimensional (quantum dots) graphene nanostructures show a clear route of how to overcome the gapless nature of graphene allowing the confinement of individual carriers and their control by lateral graphene gates and charge detectors. In particular, we emphasize that graphene quantum dots and double quantum dots are very promising systems for spin-based solid state quantum computation, since they are believed to have exceptionally long spin coherence times due to weak spin-orbit coupling and weak hyperfine interaction in graphene. 相似文献
38.
S. MiddelkampJ.J. Chang C. HamnerR. Carretero-González P.G. Kevrekidis V. AchilleosD.J. Frantzeskakis P. SchmelcherP. Engels 《Physics letters. A》2011,375(3):642-646
We explore the stability and dynamics of dark-bright (DB) solitons in two-component elongated Bose-Einstein condensates by developing effective one-dimensional vector equations and solving the three-dimensional Gross-Pitaevskii equations. A strong dependence of the oscillation frequency and of the stability of the DB soliton on the atom number of its components is found; importantly, the wave may become dynamically unstable even in the 1D regime. As the atom number in the dark-soliton-supporting component is further increased, spontaneous symmetry breaking leads to oscillatory dynamics in the transverse degrees of freedom. Moreover, the interactions of two DB solitons are investigated with an emphasis on the importance of their relative phases. Experimental results showcasing multiple DB soliton oscillations and a DB-DB collision in a Bose-Einstein condensate consisting of two hyperfine states of 87Rb confined in an elongated optical dipole trap are presented. 相似文献
39.
40.
Faraday waves in a cigar-shaped Bose-Einstein condensate are created. It is shown that periodically modulating the transverse confinement, and thus the nonlinear interactions in the BEC, excites small amplitude longitudinal oscillations through a parametric resonance. It is also demonstrated that even without the presence of a continuous drive, an initial transverse breathing mode excitation of the condensate leads to spontaneous pattern formation in the longitudinal direction. Finally, the effects of strongly driving the transverse breathing mode with large amplitude are investigated. In this case, impact-oscillator behavior and intriguing nonlinear dynamics, including the gradual emergence of multiple longitudinal modes, are observed. 相似文献