Formation of Zr I and II lines under non-LTE conditions of stellar atmospheres

The non-local thermodynaic equilibrium (non-LTE) line formation for the two ions of zirconium is considered through a range of spectral types when the Zr abundance varies from the solar value down to [Zr/H] = -3. The model atom was built using 148 energy levels of Zr I, 772 levels of Zr II, and the ground state of Zr III. It was shown that the main non-LTE mechnism for the minority species Zr I is ultraviolet overionization. Non-LTE leads to systematically depleted total absorption in the Zr I lines and positive abundance corrections, reaching to 0.33 dex for the solar metallicity models. The excited levels of Zr II are overpopulated relative to their thermodynamic equilibrium populations in the line formation layers due to radiative pumping from the low-excitation levels. As a result, the line source function exceeds the Planck function leading to weakening the Zr II lines and positive non-LTE abundance corrections. Such corrections grow towards lower metallicity and lower surface gravity and reach to 0.34 dex for Teff = 5500 K, log g = 2.0, [M/H] = -2. As a test and first application of the Zr I-Zr II model atom, Zr abundance was determined for the Sun on the basis of 1D LTE model atmosphere. Lines of Zr I and Zr II give consistent within the error bars non-LTE abundances, while the difference in LTE abundances amounts to 0.28 dex. The solar abundance of zirconium obtained with the MAFAGS solar model atmosphere is log eps(Zr) = 2.63+-0.07.Comment: published in Astron. Letters, 36, 664 (2010); Erratum was submitte

Structure and emission of highly ionized atoms

After a brief review concerning the production of highly ionised atoms and the various radiation phenomena caused by ionised species in plasmas, the internal structure of atoms and ions and their oscillator strengths are discussed in detail as a function of the nuclear charge. Special attention is paid to many-electron systems which show strong restructuration effects in their level system accompanied by irregularities of the oscillator strengths of individual spectral lines. These irregularities are caused by different effects such as level crossing and configuration interaction. Relativistic effects play an important role in the ground complex of many-electron systems. Examples are given which show the close relation between level restructurating and change of the oscillator strengths within given isoelectronic sequences as a function of nuclear charge. The influence of very strong magnetic fields on the level structure and on the oscillator strenghts of hydrogen-like species is also discussed

ATOMIC, IONIC AND MOLECULAR DATA IN THERMO-NUCLEAR FUSION RESEARCH

All high temperature hydrogen (isotopes) plasmas investigated in the frame of thermo-nuclear fusion research contain impurities like carbon, oxygen, iron,... These particles influence the plasma properties and give rise to additional undesired energy losses. It is shown how the atomic properties enter into the general balance equations describing a plasma. These equations serve for deriving the ignition and Lawson condition of a D-T fusion reactor as a function of impurity concentration and element. Graphical representations show how the fusion conditions depend on impurities. It follows a discussion of the equations applied in the spectroscopic diagnostics of plasmas and especially for determining the impurity concentrations by spectroscopic means. All equations are formulated in terms of relevant atomic data. The last section deals with molecular data which are of interest in thermo-nuclear fusion research

INFLUENCE OF BOUNDARY LAYER OF A Al-SEEDED SHOCK-HEATED PLASMA ON THE PROFILES OF THE Al I RESONANCE LINES

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