Ljubinko M. Ignjatović
University of Belgrade
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Featured researches published by Ljubinko M. Ignjatović.
Astrophysical Journal Supplement Series | 2011
A. A. Mihajlov; Ljubinko M. Ignjatović; V. A. Sreckovic; Milan S. Dimitrijevic
In this paper, the influence of chemi-ionization processes in H*(n ≥ 2) + H(1s) collisions, as well as the influence of inverse chemi-recombination processes on hydrogen atom excited-state populations in solar photosphere, are compared with the influence of concurrent electron-atom and electron-ion ionization and recombination processes. It has been found that the considered chemi-ionization/recombination processes dominate over the relevant concurrent processes in almost the whole solar photosphere. Thus, it is shown that these processes and their importance for the non-local thermodynamic equilibrium modeling of the solar atmosphere should be investigated further.
Journal of Physics: Conference Series | 2012
A. A. Mihajlov; V. A. Sreckovic; Ljubinko M. Ignjatović; Milan S. Dimitrijevic; A. Metropoulos
The aim of this research is to show that the radiative processes in strongly non- symmetric ion- atom collisions significantly influence on the opacity of the solar photosphere in UV region. Within this work only the He+H+ and H+A+ ion-atom systems, where A is the atom of one of the metal (Mg, Si and Al), are taken in to account. It is caused by the fact that the needed characteristics of the corresponding molecular ions, i.e. molecular potential curves and dipole matrix elements, have been determined by now. Here the non-symmetric radiative processes are considered under the conditions characterizing the non-LTE standard model of the solar atmosphere (Vernazza J, Avrett E and Loser R 1981 ApJS 45 635), which gives the possibility to perform all needed calculations and determined the corresponding spectral absorption coefficients. It is shown that the examined processes generate rather wide quasi-molecular absorption bands in the UV and VUV regions, whose intensity is comparable and sometimes even larger than the intensity of known ones caused by the H+H+ radiative collision processes, which are included now in the solar atmosphere models. Consequently, the presented results suggest that the non-symmetric ion-atom absorption processes have to be also included in standard models of the solar atmosphere.
Baltic Astronomy | 2011
A. A. Mihajlov; Ljubinko M. Ignjatović; V. A. Sreckovic; Milan S. Dimitrijevic
Abstract The chemi-ionization processes in atom - Rydberg atom collisions, as well as the corresponding chemi-recombination processes, are considered as factors of influence on the atom exited-state populations in weakly ionized layers of stellar atmospheres. The presented results are related to the photospheres of the Sun and some M red dwarfs, as well as weakly ionized layers of DB white dwarf atmospheres. It has been found that the mentioned chemi-ionization and recombination processes dominate over the concurrent electron-atom and electron-ion ionization and recombination processes in all parts of the considered stellar atmospheres. The obtained results demonstrate the fact that the considered processes must have significant influence on the optical properties of stellar atmospheres. It is shown that these processes and their importance for non-local thermodynamic equilibrium (non-LTE) modeling of the solar atmospheres should be investigated further.
Proceedings of the International Astronomical Union | 2016
V. A. Sreckovic; Darko Jevremović; Veljko Vujčić; Ljubinko M. Ignjatović; N. Milovanovic; Sanja Erkapic; Milan S. Dimitrijevic
In this contribution we report the current stage of the MOLecular Dissociation (MOL-D) database which is a web service within the Serbian virtual observatory (SerVO) and node within Virtual Atomic and Molecular Data Center (VAMDC). MOL-D is an atomic and molecular (A&M) database devoted to the modelling of stellar atmospheres, laboratory plasmas, industrial plasmas etc. The initial stage of development was done at the end of 2014, when the service for data connected with hydrogen and helium molecular ions was done. In the next stage of the development of MOL-D, we include new cross-sections and rate coefficients for processes which involve species such as XH+, where X is atom of some metal. Data are important for the exploring of the interstellar medium as well as for the early Universe chemistry and for the modeling of stellar and solar atmospheres. In this poster, we present our ongoing work and plans for the future.
arXiv: Solar and Stellar Astrophysics | 2010
V. A. Sreckovic; Ljubinko M. Ignjatović; A. A. Mihajlov; Milan S. Dimitrijevic
We present the calculation of the static electrical conductivity of non‐ideal, dense, partially ionized helium plasma over a wide range of plasma parameters: temperatures 104 K<T<105 K and mass density 10−6 g/cm3<ρ<2 g/cm3. The calculations of electrical conductivity of plasma for the considered range of plasma parameters are of interest for DB white dwarf atmospheres with effective temperatures 10 000 K<Teff30 000 K.
SPECTRAL LINE SHAPES IN ASTROPHYSICS: VI Serbian Conference on Spectral Line Shapes in Astrophysics (VI SCSLSA) | 2007
A. A. Mihajlov; Darko Jevremović; Peter H. Hauschildt; Milan S. Dimitrijevic; Ljubinko M. Ignjatović
Using general stellar atmosphere code PHOENIX, the influence of chemi‐ionization and inverse chemi‐recombination processes, in H*(n)+H(1s) collisions, on the population of higher levels and consequently on profiles of Hydrogen lines in the atmospheres of late type (M) stars was studied. Obtained results are the first demonstration of the possibility to confirm the considered processes influence by direct observations of stellar spectra. It is demonstrated that it is very important to include chemi‐ionization and chemi‐recombination processes in modeling of atmospheres of late type stars, especially if one wants to use line profiles for diagnostics of stellar photospheres and lower chromospheres.
SPECTRAL LINE SHAPES IN ASTROPHYSICS: VI Serbian Conference on Spectral Line Shapes in Astrophysics (VI SCSLSA) | 2007
A. N. Klyucharev; Nikolay N. Bezuglov; Andrey A. Matveev; A. A. Mihajlov; Ljubinko M. Ignjatović; Milan S. Dimitrijevic
Chemi‐ionization processes, leading to formation of molecular ions, can play an essential role in the sequence of ion‐molecular reactions on surfaces of solid particles or in associative processes of the binary collisions leading to surprising variety of molecular formations in interstellar gas and geocosmical plasmas. The presented results may be recommended for the interpretation of experimental data and for theoretical research of geocosmical plasmas, first of all the the volcanic gases on Io.
SIXTH INTERNATIONAL CONFERENCE OF THE BALKAN PHYSICAL UNION | 2007
V. A. Sreckovic; Ljubinko M. Ignjatović; A. A. Mihajlov
In this paper we analyzed atoms influence on electro conductivity, partially ionized helium plasma, in temperature region 5 000 K – 40 000 K and pressure 0.1 – 10 atm. Electro conductivity was calculated using “Frost like” formula and Random Phase Approximation method and Semi‐Classical (SC) approximation.
Astronomy and Astrophysics | 1997
A. A. Mihajlov; Ljubinko M. Ignjatović; M. M. Vasilijevic; Milan S. Dimitrijevic
European Physical Journal D | 2017
B P Marinković; Darko Jevremović; Vladimir A. Srećković; Veljko Vujčić; Ljubinko M. Ignjatović; Milan S. Dimitrijevic; Nigel J. Mason