Lj. M. Ignjatovic

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.

The influence of H

Aims. To estimate the total contribution of the absorption processes � λ + H + (X 2 Σ + ) ⇒ H(1s) + H + and � λ + H(1s) + H + ⇒ H + + H(1s) to the opacity of Solar atmosphere in UV and VUV region, and compare it with the contribution of other relevant radiative processes included in standard models. Methods. The strict quantum-mechanical method was used for the determination of the average cross-section for the photodissociation of the molecular ion H + (X 2 Σ + ); the previously developed quasi-static method was used for determination of the corresponding spectral coefficient which characterizes the absorption charge exchange in H(1s) + H + collisions. Results. Spectral absorption coefficients characterizing the considered processes were calculated for the solar photosphere and lower chromosphere, within the 90 nm ≤ λ ≤ 370 nm spectral range; the total contribution of the considered processes to the solar opacity was estimated and compared to relevant radiative processes included in standard Solar models. Conclusions. In comparison with other absorption processes included in standard Solar models, the contribution of the considered processes in the UV and VUV regions is so important that they have to be taken into account in modeling the Solar photosphere and the lower chromosphere.

\mathsf{_{2}^{+}}

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.

- photo-dissociation and (H + H

The direct current (dc) and differential pulse (dp) polarographic reduction of fleroxacin was done in a wide pH range from 2.48 to 13.00. The appropriate buffer choice was made for its dp polarographic determination in a range from 1.845 to 16.926 microg /ml, at pH 8.50. The adsorptive properties of fleroxacin were investigated in order to achieve an increase in sensitivity and a possibility of fleroxacin determination by applying the adsorptive stripping voltammetric method. The adsorptive processes at the hanging mercury drop electrode were investigated in Britton-Robinson and borate buffers. Adsorptive preconcentration followed by differential-pulse cathodic stripping showed one wave at approximately - 1.1 V being the most sensitive for analytical determination of fleroxacin. Two linear ranges were obtained, the first one from 18.465 to 258.51 ng/ml, and the second one from 3.693 to 18.465 ng/ml.

\mathsf{^{+}}

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.

)- radiative collisions on the solar atmosphere opacity in UV and VUV regions

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.

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

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

Voltammetric methods for analytical determination of fleroxacin in Quinodis® tablets

^{+}

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

collisions together with the process of ion HeH

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

^{+}