THEORETICAL STUDYING EXCITED STATES SPECTRUM OF THE YTTERBIUM WITHIN THE OPTIMIZED RELATIVISTIC MANY-BODY PERTURBATION THEORY

Theoretical studying spectrum of the excited states for the ytterbium atom is carried out within the relativistic many-body perturbation theory with ab initio zeroth approximation and generalized relativistic energy approach. The zeroth approximation of the relativistic perturbation theory is provided by the optimized Dirac-Kohn-Sham ones. Optimization has been fulfilled by means of introduction of the parameter to the Kohn-Sham exchange potentials and further minimization of the gauge-non-invariant contributions into radiation width of atomic levels with using relativistic orbital set, generated by the corresponding zeroth approximation Hamiltonian. The obtained theoretical data on energies E and widths W of the ytterbium excited states are compared with alternative theoretical results (the Dirac-Fock, relativistic Hartree-Fock, perturbation theories) and available experimental data. Analysis shows that the theoretical and experimental values ​​of energies are in good agreement with each other, however, the values ​​of widths differ significantly. In our opinion, this fact is explained by insufficiently accurate estimates of the radial integrals, the use of unoptimized bases, and some other approximations of the calculation.

Dew points of quaternary ethane + carbon dioxide + water + methanol mixtures — Measurement and modelling

Dew points have been measured for eight ethane + carbon dioxide + water + methanol mixtures at pressures from 0.11 to 2.17 MPa and temperatures from 249.0 to 288.7 K. The results are analysed in terms of a predictive excess-function equation of state (EF-EOS) method based on the zeroth approximation of Guggenheim's reticular model. This method can be used to adequately predict the dew points of the mixtures in the temperature and pressure ranges used in the present study. In fact, the model reproduces the experimental dew point temperature data with ≤3.1 K average absolute deviation.Key words: dew point, equation of state, excess function.

Näherungslösung einer verallgemeinerten Nernst-Planck-Gleichung für ein eindimensionales Membranmodell / Approximative Solution of a Generalized Nernst-Planck-equation for a one Dimensional Membran-model

The starting-point of this paper are generalized Nernst Planck equations, which are deduced microscopically. Using a perturbation approach a result of this equation is given for a constant external field and a membran, which has a low concentration of fixed charges. The used conditions give a zeroth approximation which describes the homogeneous electrolyte. The first approximation shows the influence of the fixed charges, the friction between ions and membran and the influence of the correlations. The flows and the concentrations are then calculated for a system with equal concentrations on both sides of the membran.