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971.
A. Birczyński Z.T. Lalowicz A.M. Szymocha M. Punkkinen E.E. Ylinen A.H. Vuorimäki 《Chemical physics》2006
Deuteron spin–lattice relaxation is studied in 5% and 100% deuterated ammonium hexachlorostannate and perchlorate. The relaxation rate is observed to be independent of deuteration down to temperatures slightly lower than that of the maximum. At lower temperatures the rate of the 5% deuterated sample exceeds that of the 100% deuterated sample by four and two orders of magnitude in ammonium hexachlorostannate and perchlorate, respectively. The angular dependence of the deuteron relaxation rate in 5% deuterated ammonium hexachlorostannate at 6 K is explained in terms of existing models on quadrupolar relaxation. In 5% ammonium perchlorate one hydrogen equilibrium position, which lies on the preferred axis for 120° rotations, has a larger probability to be occupied by the deuteron of NH3D+ ions. The deuterons at the other positions are still performing rotational jumps about the preferred C3 axis and also about the other threefold axes, although at a slower rate. Such observations require a reconsideration of the relaxation process. A somewhat more general expression is derived for the relaxation rate, which agrees with the experimentally observed angular dependence for 5% deuterated ammonium perchlorate at 60 K. At lower temperatures the quadrupole coupling of the deuterons at the preferred axis may become practically time-independent. Then a significant contribution to the relaxation rate can be provided by the deuteron–proton magnetic dipolar interaction, which is still fluctuating fast via the rotation of the three protons about the axis through the stationary deuteron. 相似文献
972.
W. Sierpiński 《Monatshefte für Mathematik》1928,35(1):239-242
Sans résumé 相似文献
973.
974.
J. Bukowski R. Kański M. Kańska 《Journal of Radioanalytical and Nuclear Chemistry》2002,254(3):613-618
The kinetic isotope effect (KIE) was applied in the study of the mechanism of bromine elimination from p-methyl-erythro-a,b-dibromocinnamic acid, successively labeled at the a and b carbons. The large 14C KIE for the b-position and small KIE for the a one of side chain of p-methyl-erythro-a,b-dibromocinamic acid proves that elimination of bromine leading to the formation of (E)-p-methylcinnamic acid proceeds via the E1 mechanism. 相似文献
975.
J. Łojewska A. Lubańska P. Miśkowiec T. Łojewski L.M. Proniewicz 《Applied Physics A: Materials Science & Processing》2006,83(4):597-603
This study deals with the quantitative and qualitative interpretation of transmission FTIR spectra of aged model paper samples to prepare the basis for a kinetic model of cellulose degradation involving mixed hydrolytic and oxidative mechanism. The ageing experiments were performed in situ under various conditions (pure water vapour, dried air, 100, 150 °C) to discriminate between hydrolytic and oxidative paths. Our focus was on the spectra between 1500–1900 cm-1, where the products of paper ageing appear in the form of various carbonyl groups. A procedure of spectra standardization was used to interpret the bands area in terms of the conversion of carbon atoms in cellulose. From the time evolution of the bands the overall kinetic curves were generated. The positions of the carbonyl bands were verified by independent experiments and theoretical calculations (DFT method). A simple model involving a hydrolytic reaction route and first order kinetics was positively tested on the available experimental basis. PACS 81.05.-t; 82.20.Wt; 87.15.Rn 相似文献
976.
Mixed Norm and Multidimensional Lorentz Spaces 总被引:2,自引:0,他引:2
In the last decade, the problem of characterizing the normability of the weighted Lorentz spaces has been completely solved
([16], [7]). However, the question for multidimensional Lorentz spaces is still open. In this paper, we consider weights of
product type, and give necessary and sufficient conditions for the Lorentz spaces, defined with respect to the two-dimensional
decreasing rearrangement, to be normable. To this end, it is also useful to study the mixed norm Lorentz spaces. Finally,
we prove embeddings between all the classical, multidimensional, and mixed norm Lorentz spaces.
Research partially supported by KAW 2000.0048 and STINT KU 2002-4025.
Research partially supported by Grants MTM2004-02299, 2005SGR00556 and The Swedish Research Council no. 624-2003-571. 相似文献
977.
E. Grodner A. A. Pasternak Ch. Droste T. Morek J. Srebrny J. Kownacki W. Płóciennik A. A. Wasilewski M. Kowalczyk M. Kisieliński R. Kaczarowski E. Ruchowska A. Kordyasz M. Wolińska 《The European Physical Journal A - Hadrons and Nuclei》2006,27(3):325-340
Lifetimes of yrast levels with spins Iπ = 23/2--43/2- in 131La populated in the 122Sn(14N, 5n) reaction at a beam energy of 70MeV are measured by the Doppler Shift Attenuation method. A model of side-feeding population
is presented. The model parameters are determined in an experiment based on the lineshape of γ-transitions from two highest
spin levels and from the intensity distribution along the yrast band. The properties of the h11/2 band in 131La are compared with the theoretical predictions obtained in the framework of the Core-Quasi-Particle Coupling and the self-consistent
Total Routhian Surface models. 相似文献
978.
Piotr ?y?wa Ma?gorzata Kwiatkowska Piotr Kie?basiński Alexander Betz Annie-Claude Gaumont 《Tetrahedron letters》2007,48(3):351-355
A chiral racemic 2-phosphono-2,3-didehydrothiolane sulfoxide was used as a Michael acceptor in the reactions with several nucleophiles, in particular thiols. In most cases the reactions were fully diastereoselective. The relative configuration of the resulting adducts was determined. 相似文献
979.
Wojciech Jankowski Maria Gdaniec Tadeusz Pooski 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(8):o492-o494
The crystal structure of the title compound, benzamide–2,3,4,5,6‐pentafluorobenzoic acid (2/1), 2C7H7NO·C7HF5O2, consists of centrosymmetric hexameric supermolecules composed of four amide and two carboxylic acid molecules connected via O—H⋯O and N—H⋯O hydrogen bonds. No phenyl–perfluorophenyl π–π stacking interactions are observed in this cocrystal. 相似文献
980.