Chemi-ionization in Solar Photosphere: Influence on the Hydrogen Atom excited States Population

In this paper, the influence of chemi-ionization processes in $H^*(n \ge 2) + H(1s)$ 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-LTE modeling of the solar atmosphere should be investigated further

Symmetric Atom–Atom and Ion–Atom Processes in Stellar Atmospheres

We present the results of the influence of two groups of collisional processes (atom–atom and ion–atom) on the optical and kinetic properties of weakly ionized stellar atmospheres layers. The first type includes radiative processes of the photodissociation/association and radiative charge exchange, the second one the chemi-ionisation/recombination processes with participation of only hydrogen and helium atoms and ions. The quantitative estimation of the rate coefficients of the mentioned processes were made. The effect of the radiative processes is estimated by comparing their intensities with those of the known concurrent processes in application to the solar photosphere and to the photospheres of DB white dwarfs. The investigated chemi-ionisation/recombination processes are considered from the viewpoint of their influence on the populations of the excited states of the hydrogen atom (the Sun and an M-type red dwarf) and helium atom (DB white dwarfs). The effect of these processes on the populations of the excited states of the hydrogen atom has been studied using the general stellar atmosphere code, which generates the model. The presented results demonstrate the undoubted influence of the considered radiative and chemi- ionisation/recombination processes on the optical properties and on the kinetics of the weakly ionized layers in stellar atmospheres

The Screening Characteristics of the Dense Astrophysical Plasmas: The Three-Component Systems

As the object of investigation, astrophysical fully ionized electron-ion plasma is chosen with positively charged ions of two different kinds, including the plasmas of higher non-ideality. The direct aim of this work is to develop, within the problem of finding the mean potential energy of the charged particle for such plasma, a new model, self-consistent method of describing the electrostatic screening. Within the presented method, such extremely significant phenomena as the electron-ion and ion-ion correlations are included in the used model. We wish to draw attention to the fact that the developed method is suitable for astrophysical applications. Here we keep in mind that in outer shells of stars, the physical conditions change from those that correspond to the rare, practically ideal plasma, to those that correspond to extremely dense non-ideal plasma

Photodestruction of Diatomic Molecular Ions: Laboratory and Astrophysical Application

In this work, the processes of photodissociation of some diatomic molecular ions are investigated. The partial photodissociation cross-sections for the individual rovibrational states of the diatomic molecular ions, which involves alkali metals, as well as corresponding data on molecular species and molecular state characterizations, are calculated. Also, the average cross-section and the corresponding spectral absorption rate coefficients for those small molecules are presented in tabulated form as a function of wavelengths and temperatures. The presented results can be of interest for laboratory plasmas as well as for the research of chemistry of different stellar objects with various astrophysical plasmas

A study of high-frequency properties of plasma and the influence of electromagnetic radiation from IR to XUV

On the basis of calculated values for the conductivity in an external electric field, we determined the high-frequency characteristics of plasmas under extreme conditions (e. g. dense plasma focus device). The examined range of frequencies covers the IR, visible, UV, XUV up to X regions and the considered electronic number density and temperature are in the ranges of 1021 cm-3 ≤ Ne ≤ 5×1024 cm-3 and 2×104 K ≤ T ≤ 106 K, respectively. The data obtained using this method are important for plasma focus research, laboratory plasma research, investigation of atmosphere plasmas of astrophysical objects like white dwarfs with different atmospheric compositions. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 176002 Grant no. III44002

The role of some collisional processes in AGNs: Rate coefficients needed for modeling

International audienceThe importance of some atom hydrogen collisions in AGN has been investigated. The results are useful for better estimation of the hydrogen Balmer lines fluxes, which usage for effective temperature diagnostics in astrophysical plasma is limited by errors from the line formation models. The data could be also useful for modeling cooler and denser parts of AGN BLR clouds, as well as for the investigation of Rydberg states of hydrogen and for the study of their influence during the cosmological recombination epoch. The results of the present work suggest that the investigated processes are of interest for the research and modeling of such media

Radiative and Collisional Molecular Data and Virtual Laboratory Astrophysics

Spectroscopy has been crucial for our understanding of physical and chemical phenomena. The interpretation of interstellar line spectra with radiative transfer calculations usually requires two kinds of molecular input data: spectroscopic data (such as energy levels, statistical weights, transition probabilities, etc.) and collision data. This contribution describes how such data are collected, stored, and which limitations exist. Also, here we summarize challenges of atomic/molecular databases and point out our experiences, problems, etc., which we are faced with. We present overview of future developments and needs in the areas of radiative transfer and molecular data

The Collisional Atomic Processes of Rydberg Hydrogen and Helium Atoms: Astrophysical Relevance

Elementary processes in astrophysical environments traditionally attract researchers’ attention. We present the data needed for the inclusion of the specific atomic collisional processes in the investigation of the optical and kinetic properties of weakly ionized stellar atmosphere layers. The first type of processes are collisional ionisation (chemi-ionization) processes, and the second ones are excitation and de-excitation (i.e., (n-n′)-mixing processes). We give the rate coefficients of the aforementioned processes for the conditions that exist in the solar photosphere, the atmosphere of DB white dwarfs, M-type red dwarfs, etc

Data for Photodissociation of Some Small Molecular Ions Relevant for Astrochemistry and Laboratory Investigation

The calculated photodissociation data of some small molecular ions have been reported. The cross-sections and spectral rate coefficients data have been studied using a quantum mechanical method. The plasma parameters, i.e., conditions, cover temperatures from 1000 to 20,000 K and wavelengths in the EUV and UV region. The influence of temperature and wavelength on the spectral coefficients data of all of the investigated species have been discussed. Data could also be useful for plasma diagnostics in laboratory, astrophysics, and industrial plasmas for their modelling

The Rydberg atom-atom collisions: Chemi-ionization cross-sections and rate coefficients in alkali-metal astrophysical and low-temperature laboratory plasmas

In this manuscript, the chemi-ionization (CI) processes in atom - Rydberg atom collisions are examined. We obtained the cross-sections, as well as rate coefficients for CI processes in potassium and sodium collisions for principal quantum numbers 5⩽n⩽25 in the 500 K ⩽T⩽1500 K temperature region. The presented data could be useful for the improvement of analysis and modelling of weakly ionized layers of different atmospheres and cosmic objects where these and other CI processes could change excited state populations and the free electron density, consequently affecting the optical characteristics