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951.
T. Brodzinski H. -D. Kronfeldt R. Winkler 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1987,6(4):363-364
The J-dependence of the isotope shift (IS) in the term a6D of the Eu I configuration 4f75d6s was determined to be: z5d(6D)=+34.5(1.5) MHz. This proves that in the phenomenological interpretation of the IS distinct parameters znl(mL) for the J-dependence in one term are necessary. 相似文献
952.
Theis M Thalhammer G Winkler K Hellwig M Ruff G Grimm R Hecker Denschlag J 《Physical review letters》2004,93(12):123001
We demonstrate optical tuning of the scattering length in a Bose-Einstein condensate as predicted by Fedichev et al. [Phys. Rev. Lett. 77, 2913 (1996)]. In our experiment, atoms in a 87Rb condensate are exposed to laser light which is tuned close to the transition frequency to an excited molecular state. By controlling the power and detuning of the laser beam we can change the atomic scattering length over a wide range. In view of laser-driven atomic losses, we use Bragg spectroscopy as a fast method to measure the scattering length of the atoms. 相似文献
953.
Arynes, which are formally derived from aromatic rings by abstraction of two hydrogen atoms, have been a focus of organic chemistry for 100 years. In contrast to ortho-benzyne, which is mentioned in almost every introductory textbook on organic reaction mechanisms as a reactive intermediate of nucleophilic aromatic substitution, the meta and para isomers were regarded as rather exotic until recently. This situation has changed dramatically with the discovery of the enediyne antibiotics, a promising new class of antitumor drugs, and has aroused the interest of research groups from all branches of chemistry. Nowadays, arynes and related compounds are among the most intensively studied systems in chemistry. However, many aspects of the chemistry of these reactive intermediates are not well understood yet. In this review we outline the historical developement with an emphasis on recent progress in this challenging field of research. 相似文献
954.
The cover picture shows schematically the formation of the phenyl cation by photoionization of halobenzenes and its further reaction with nitrogen to give the benzene diazonium ion. The phenyl cation, as well as its reaction products, could be isolated in argon matrices and characterized by IR spectroscopy. The upper part of the picture shows the argon resonance lamp used for the photoionization of the halobenzenes. The structures of the molecules shown were obtained by DFT calculations. Further details of the matrix isolation of the phenyl cation are described by M. Winkler and W. Sander on page 2014. 相似文献
955.
Experiments on high-quality GaAs (311)A two-dimensional holes at low temperatures reveal a remarkable dependence of the magnetoresistance, measured with an in-plane magnetic field ( B), on the direction of B relative to both the crystal axes and the current direction. The magnetoresistance features, and in particular the value of B above which the resistivity exhibits an insulating behavior, depend on the orientation of B. To explain the data, the anisotropic band structure of the holes and a repopulation of the spin subbands in the presence of B, as well as the coupling of the orbital motion to B, need to be taken into account. 相似文献
956.
M. Haas E. Realo H. Winkler W. Meyer‐Klaucke A.X. Trautwein 《Hyperfine Interactions》2000,125(1-4):189-195
An expression for the amplitude of a pulse of synchrotron radiation coherently scattered in the forward direction by a Mössbauer absorber consisting of randomly oriented paramagnetic ironcontaining molecules (for example, a frozen solution of a 57Fe protein) in an applied magnetic field is derived from the theory of optics. It is assumed that the hyperfine splittings present in the Mössbauer nuclei can be described in the framework of the spinHamiltonian formalism. In the general case of a thick Mössbauer sample of this kind the response on an incident monochromatic and fully polarized beam cannot be given analytically because of the integrations involved. How nuclear forwardscattering for this general case is evaluated in the program package called SYNFOS is outlined. 相似文献
957.
Many-body effects in solids are ultimately related to the correlation among electrons, which can be probed by double photoelectron emission. We have investigated the electron pair emission from a Cu(111) surface upon photon absorption. We are able to observe for the first time the full extension and shape of a depletion zone around the fixed emission direction of one electron. It has an angular extension of approximately 1.2 rad, which is independent of the electron energy. 相似文献
958.
Hienola AI Winkler PM Wagner PE Vehkamäki H Lauri A Napari I Kulmala M 《The Journal of chemical physics》2007,126(9):094705
Using the classical nucleation theory corrected with line tension and experimental data of heterogeneous nucleation of n-nonane, n-propanol, and their mixture on silver particles of three different sizes, the authors were able to estimate the line tensions and the microscopic contact angles for the above mentioned systems. To do this they applied generalized Young's equation for the line tension and calculated the interfacial tensions using Li and Neumann's equation [Adv. Colloid Interface Sci. 39, 299 (1992)]. It has been found that, for both unary and binary systems, the line tension is negative and the resulting microscopic contact angle derived from experimental nucleation data is most of the time larger than the macroscopic one. This is in contrast to earlier studies where the influence of line tension has not been accounted for. The values of the three phase contact line tension obtained in this way are of the same order of magnitude as the estimations for other systems reported in literature. The line tension effect also decreases considerably the nucleation barrier. 相似文献
959.
Herndl A Marzban G Kolarich D Hahn R Boscia D Hemmer W Maghuly F Stoyanova E Katinger H Laimer M 《Electrophoresis》2007,28(3):437-448
The importance of apple allergens has been repeatedly emphasized, and their presence has been confirmed both in pollen and in fruits. In the present study, a combination of proteomic tools have been used to build a complete allergen map of apple. The water-soluble fraction of an apple extract was precipitated using a phenol-based procedure and separated by 2-DE. Initially four previously classified allergens, Mal d 1, Mal d 2, Mal d 3 and Mal d 4, could be identified in Western blots with polyclonal rabbit antibodies directed to the four respective allergens, and subsequently matched to the bands recognized by several patient sera. Further, all four known apple allergens were localized on a 2-DE map and they were matched with spots recognized by sera of patients with different allergic patterns. Moreover, a new, putative allergen could be identified using MS. We evaluated the influence of post-translational modifications and the immunoreactivity under different analytical conditions. The comparison of different visualization methods for 2-DE gels and blots revealed that even very low concentrations of the intact epitopes are detectable by IgEs of patients, and therefore might be sufficient to trigger allergic symptoms in sensitized individuals. 相似文献
960.