Influence of Rydberg atom-atom collisional and (n-n')-mixing processes on optical properties of astrophysical and low-temperature laboratory plasmas (original) (raw)
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Monthly Notices of the Royal Astronomical Society, 2016
In this paper, the rate coefficients of the chemi-ionization processes in H(1s) + H*(n, l) and He(1s 2) + He * (n, l) collisions (where the principal quantum number n 1) are determined for the first time, taking into account the influence of the corresponding (n − n)-mixing processes. It is demonstrated that the inclusion of (n − n) mixing in the calculation influences the values of chemi-ionization rate coefficients significantly, particularly in the lower part of the block of Rydberg states. The interpretation of this influence is based on two existing methods of describing inelastic processes in symmetrical atom-Rydberg-atom collisions. The calculations of the chemi-ionization rate coefficients are performed for the temperature region that is characteristic of solar and DB white-dwarf atmospheres.
Proceedings of The International Astronomical Union, 2003
Results of our investigations of the influence of radiation, chemi-ionization and chemi-recombination processes in atom-atom and ion-atom collisions (in the case of the symmetric atom-atom and ion-atom systems) in stellar hydrogen and helium plasmas are presented. The considered ion-atom radiation processes influence significantly on the optical characteristics of stellar plasma, and the considered chemi-ionization/recombination processes on the excited atomic energy level populations, as well as on the electron density. The consequence of the obtained results is that they should be taken into account for the modeling of photosohere and lower chromosphere of the Sun and similar star (hydrogen case) and white dwarfs atmospheres (helium case).
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.
Journal of Cluster Science, 2012
In this paper the history and the current state of research of the chemi-ionization processes in atom-Rydberg atom collisions is presented. The principal assumptions of the model of such processes based on the dipole resonance mechanism, as well as the problems of stochastic ionization in atom-Rydberg atom collisions, are exposed. The properties of the collision kinetics in atom beams of various types used in contemporary experimentations are briefly described. Results of the calculation of the chemi-ionization rate coefficients are given and discussed for the range of the principal quantum number values 5 ≤ n ≤ 25. The role of the chemi-ionization processes in astrophysical and laboratory low-temperature plasmas, and the contemporary methods of their investigation are described. Also the directions of further research of chemi-ionization processes are discussed in this paper.
The significance of (n − n )-mixing processes in H ∗ (n) + H(1s) collisions, for the principal quantum number n ≥ 4, in the Solar photosphere and lower chromosphere has been investigated. These processes have been treated by the mechanism of resonant energy exchange within the electron component of the considered collision system. These processes must have significant influence in comparison with corresponding electron-atom collision processes on the populations of hydrogen Rydberg atoms in weakly ionized layers of the Solar atmosphere (ionization degree of the order of 10 −4 ). From the results obtained it follows that the examined (n − n )-mixing processes have to be included in any modelling and investigation of Solar plasma, especially in the region of the temperature minimum in the Solar photosphere.
Journal of Physics: Conference Series, 2019
Non-LTE modelling requires accurate atomic data e.g. collisional excitation and ionization cross-sections and rate coefficients. In order to improve the modeling of the solar photosphere, as well as to model atmospheres of other similar and cooler stars where the main constituent is also hydrogen, it is necessary to take into account the influence of all the relevant collisional processes on the excited-atom populations in weakly ionized hydrogen plasmas. In this context 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 atmospheres layers. The ionization processes in collisions of excited hydrogen atoms with atoms in ground states were considered for the principal quantum numbers 2 ≤ n ≤ 20 and temperatures 4000 K ≤ T ≤ 20000 K.
In this paper we have presented some of our preliminary results illustrating the influence of a group of symmetrical chemical ionization and chemical recombination processes on the populations of hydrogen-atom Rydberg states in low-temperature layers of stellar photospheres and a part of chromospheres. These processes are H Ã (n) þ H(1s) ! H þ 2 þ e=H(1s) þ H þ e and H 2 þ e ! H (n) þ H(1s), H(1s) þ H þ e ! H (n) þ H(1s), where H Ã (n) is the hydrogen atom in a Rydberg state with the principal quantum number n ) 1, and H þ 2 is the hydrogen molecular ion in a weakly bound rovibrational state. The mentioned processes have been considered within the framework of the semiclassical approximation, developed in several previous papers. Their influence on the populations of hydrogen-atom Rydberg states has been investigated by direct inclusion in a computer code for stellar atmosphere modelling. Here we present some of our preliminary results for the M dwarf atmospheres. Our results show that the influence of these processes is significant for the considered stellar atmospheres, so that they should be taken into account for their modelling.
Astronomy and Astrophysics, 2003
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: , 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 . We present results for an M dwarf atmosphere with T eff = 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 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.