A. A. Mihajlov

The realization of Abel's inversion in the case of discharge with undetermined radius

Abstract A new method for the determination of the local plasma emissivity on the basis of measuring of the radiation intensity is presented. The method is related to the axial symmetric discharges with undefined radius (free burning arcs, etc.). In this method, the experimental profile of the radiative intensity is approximated by the linear combination of Gaussian functions, while the requested plasma emissivity is obtained in a similar oblique. The essence of the presented method lies in the procedure of determination of the coefficients in this linear combinations, as well as the parameters by which the exponents of Gaussian functions are expressed. The method was tested on a large number of examples which are related to almost all practically important cases of the profiles of local plasma emissivity. It was shown that the method works with high precision, which makes it a certain tool for an operative laboratorial application.

Rate coefficients of collisional H – H*(n) ionization and H – H+ – e and H2+ – e recombination

On the basis of a semi-classical theory, the rate coefficients of collisional H – H*(n) ionization and recombination during electron scattering on H – H+ complexes and H2+ ions were determined in this paper. The calculations were carried out in the case of non-equilibrium hydrogen plasma with atomic temperature Ta and electronic temperature Te, in the domains 2000 K ≤ Ta ≤ 10 000 K and 2000 K ≤ Te ≤ 30 000 K, with the principal quantum number 4 ≤ n ≤ 10. In the paper we have also determined the conditions under which these processes are important for the kinetics of weakly ionized hydrogen plasma.

Rydberg atoms in astrophysics

Elementary processes in astrophysical phenomena traditionally attract researchers attention. At first this can be attributed to a group of chemi-ionization processes in Rydberg atom collisions with ground state parent atoms. This processes might be studied as a prototype of the elementary process of the radiation energy transformation into electrical one. The studies of nonlinear mechanics have shown that so called regime of dynamic chaos should be considered as typical, rather than exceptional situation in Rydberg atoms collision. From comparison of theory with experimental results it follows that a such kind of stochastic dynamic processes, occurred during the single collision, may be observed.

Coulomb conductivity of strongly coupled plasmas

Abstract The Coulomb conductivity of strongly coupled plasmas is calculated. The transition to the Spitzer formula is analyzed. A comparison with the available experimental data is made.

Influence of chemi-ionization and chemi-recombination processes on the population of hydrogen Rydberg states in atmospheres of late type dwarfs

We study the influence of a group of chemi-ionization and chemi-recombination processes on the populations of higher states of hydrogen in the layers of a stellar atmosphere. The group of processes includes ionization: H*(n) + H(1s) ⇒ H + 2 +e, H*(n)+H(1s) ⇒ H(1s)+H + +e, and inverse recombination: H + 2 +e ⇒ H*(n)+H(1s), H(1s)+H + +e ⇒ H*(n)+H(1s), where H*(n) is the hydrogen atom in a state with the principal quantum number n » 1, and H + 2 is the hydrogen molecular ion in a weakly bound rho-vibrational state of the ground state. These processes have been treated within the framework of the semi-classical approximation, developed in several previous papers, and have been included in the general stellar atmosphere code PHOENIX. We present results for an M dwarf atmosphere with T e f f = 3800 K and find that the inclusion of chemi-ionization and chemi-recombination processes is significant in the low temperature parts of the atmosphere.

The non-symmetric ion–atom radiative processes in the stellar atmospheres

The aim of this research is to show that the processes of absorption charge exchange and photoassociation in A + B + collisions together with the processes of AB + photodissociation in the case of strongly non-symmetric ion–atom systems, significantly influence the opacity of stellar atmospheres in ultraviolet (UV) and extreme UV (EUV) region. In this work, the significance of such processes for solar atmosphere is studied. In the case of the solar atmosphere the absorption processes with A = H and B = Mg and Si are treated as dominant ones, but the cases A = H and B = Al and A = He and B = H are also taken into consideration. The choice of just these species is caused by the fact that, of the species relevant for the used solar atmosphere model, it was only for them that we could determine the necessary characteristics of the corresponding molecular ions, i.e. the molecular potential curves and dipole matrix elements. It is shown that the efficiency of the examined non-symmetric processes within the rather wide corresponding quasi-molecular absorption bands in the far-UV and EUV regions is comparable and sometimes even greater than the intensity of the known symmetric ion–atom absorption processes, which are included now in the models of the solar atmosphere. Consequently, the presented results suggest that the non-symmetric ion–atom absorption processes also have to be included ab initio in the corresponding models of the stellar atmospheres.

Influence of ion-atom collisions on the recombination of electrons

AbStraEt. We show that for the study of recombination of ions and electrons in weakly ionized lowtemperature hydrogen plasmas, the processes H+H++e+H+H*(n) and H:+e+H+H*(n) must both be considered Since their contributions arc comparable. A simple method for the calculation of the corresponding rate coefficients is presented.

The ion-atom absorption processes as one of the factors of the influence on the sunspot opacity

As a continuation of the previous investigations of the symmetric and strongly nonsymmetric ion-atom absorption processes in the far UV region within the models of the quiet Sun photosphere, these processes are studied here within a model of the sunspot. Here we mean the absorption processes in the H(1s)+H + and H(1s) + X + collisions and the processes of the photo-dissociation of the H + and HX + molecular ions, where X is one of the metal atoms: X =Na, Ca, Mg, Si and Al. Obtained results show that the influence of the considered ion-atom absorption processes on the opacity of sunspots in the considered spectral region (110 nm . � . 230 nm) is not less and in some parts even larger than the influence of the referent electron-atom processes. In such a way, it is shown that the considered ion-atom absorption processes should be included ab initio in the corresponding models of sunspots of solar-type and near solartype stars. Apart of that, the spectral characteristics of the considered non-symmetric ion-atom absorption processes (including here the case X = Li), which can be used in some further applications, have been determined and presented within this work.

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 ≥ 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.

Absorption non-symmetric ion–atom processes in helium-rich white dwarf atmospheres

In this work the processes of absorption charge-exchange and photo-association in He+H