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21.
Petr Šeba 《Letters in Mathematical Physics》1988,16(1):51-59
The method of complex scaling, usually used in atomic and molecular resonance calculations, is generalized to the Dirac equation. It is shown that Dirac resonances are associated with nonreal eigenvalues of the scaled Dirac Hamiltonian. The perturbation theory for the resonance parameters is also discussed. 相似文献
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V. A. Petržílka 《Czechoslovak Journal of Physics》1989,39(12):1372-1377
The amplification of lower hybrid (LH) driven current of various profiles has been found. The results strongly depend on the plasma temperature profile, on the LH current profile, and on the magnitude of the particle diffusion flux.This work was started during the visit of the author in the I. V. Kurchatov Institute of Atomic Energy, Moscow. The author thanks IAE for hospitality, and V. Parail, G. V. Pereverzev, A. Smoljakov and R. Klíma for many useful and critical discussions. 相似文献
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Crystal Structure of AgCu3Cu(AsO4)3 and its Structural Relations to AgCo3H2(AsO4)3 and AgZn3H2 (AsO4)3 The compound AgCu3Cu(AsO4)3 was synthesized and investigated by X-rays. It crystallizes in the monoclinic space group C2/c with a = 1 212.7(2), b = 1 249.0(2), c = 727.8(1) pm, β = 117.94(1)°, Z = 4. The structure is closely related to the structures of AgCo3H2(AsO4)3 and AgZn3H2(AsO4)3. Only two hydrogen atoms are replaced by an additional copper atom forming a copper coordination square instead of two hydrogen bridges. The remaining copper atoms are sixfold coordinated with the generally observed Jahn-Teller distortion. Whereas in AgCo3H2(AsO4)3 and AgZn3H2(AsO4)3 silver has a (4+4) coordination, it is in this compound distinctly eightfold coordinated. 相似文献
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On P? P Containing Cyclic Compounds. II. Reaction of N,N'-dimethylthiourea with phenyl dichlorophosphane yields 1.4-dimethyl-2. 3-diphenyl-1.4.2.3-diazadiphospholidine-5-thione-2-sulfide ( II ). The compound is characterized by its nmr, vibration and mass spectra as well as the results of an X-ray structural analysis. Byproduct of the reaction is N-(N,N'-dimethylcarbamimidoyl)-N,N'-dimethyl thiourea hydrochloride ( III ), which crystallizes with pyridinium chloride. Molecular and crystal structure are reported. With methyl dichlorophosphane N,N'-dimethylthiourea forms 1.2.3.4-tetramethyl-1.4.2.3-diazadiphospholidine-5-thione-2-sulfide ( IV ), which is characterized by its nmr and vibration spectra. 相似文献
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Coordination of dinitrogen to Sellmann-type iron (II) complexes in a sulfur-dominated coordination sphere, which emulates
the environment of iron centers in the FeMo-cofactor of nitrogenase, is analyzed with respect to spin states, spin barriers,
and the effect of trans-ligands. Such detailed investigations became only recently feasible when the reliability of density functional methods, which
are the only quantum chemical methods capable of describing large transition metal complexes, could significantly be improved
for the calculation of energies for states of different spin. It is found that the actual binding energy of dinitrogen is
of sufficient magnitude for a reasonably strong fixation of N2 by Sellmann-type coordination compounds. However, potential fixation is determined by additional factors which reduce the
binding energy. One factor is the change in spin state of the N2-free metal fragment, which lowers the total energy and quenches the thermodynamic stabilization effect of the binding energy.
In addition, the metal fragment rearranges and gains even more stabilization energy for the un-coordinated state. Apart from
these thermodynamical effects, the existence of spin barriers, which must be overcome upon binding of dinitrogen, leads to
kinetical effects, which cannot be neglected. 相似文献