367 research outputs found
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 non-symmetric 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+H and H collisions and the processes of the
photo-dissociation of the H and H molecular ions, where is
one of the metal atoms: 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 \emph{ab initio} in
the corresponding models of sunspots of solar-type and near solar-type stars.
Apart of that, the spectral characteristics of the considered non-symmetric
ion-atom absorption processes (including here the case = Li), which can be
used in some further applications, have been determined and presented within
this work.Comment: Accepted in Monthly Notices of the Royal Astronomical Societ
Excitation and deexcitation processes in atom-Rydberg atom collisions in helium-rich white dwarf atmospheres
We aim to show the importance of non-elastic excitation and deexcitation
processes in collisions with the
principal quantum number for helium-rich white dwarf atmospheres. We
compare the efficiencies of these processes with those of the known non-elastic
electron- atom processes in the atmospheres of some DB
white dwarfs. We show that in significant parts of the considered atmospheres,
which contain weakly ionized layers (the ionization degree ),
the influence of the studied atom-Rydberg atom processes on excited helium atom
populations is dominant or at least comparable to the influence of the
concurrent electron--atom processes.Comment: Astronomy & Astrophysics, Accepted: 14 February 201
The influence of the radiative non-symmetric ion-atom collisions on the stellar atmospheres in VUV region
The aim of this work is to draw attention to the processes of radiative
charge exchange in non-symmetric ion-atom collisions as a factor of influence
on the opacity of stellar atmospheres in VUV region. For that purpose
calculations of the spectral absorption coefficients for several ion-atom
systems, namely: He + H and H + X, where X = Na and Li have been
performed. On chosen examples it has been established that the examined
processes generate rather wide molecular absorption bands in the VUV region,
which should be taken into account for the interpretation of data obtained from
laboratory measurements or astrophysical observations. In this paper the
potential significance is discussed of the considered radiative processes for
DB white dwarfs and solar atmospheres, as well as for the atmospheres of the
so-called lithium stars
Ion-atom radiative processes in the solar atmosphere: quiet Sun and sunspots
In the previous works the significance of the symmetric and non-symmetric
ion-atom absorption processes in far UV and EUV regions within a model of the
quiet Sun atmosphere, has been studied. The considered processes were the
processes of the photo-dissociation of the molecular ions H and
H and absorption processes in H+H and H collisions, where
denotes the metal atom. As the continuation of the previous investigation,
these processes are considered also within the corresponding sunspot model. In
this work the non-symmetric ion-atom absorption processes are considered with
Mg, Si, etc. It was analyzed the significance of such processes in far UV
and EUV regions in comparison with the concurrent absorption processes,
especially with the processes of the photo-ionization of the metal atoms (Na,
Mg, Ca, etc.) which were not included in the consideration in the case of the
quiet Sun atmosphere. From our analysis it follows that the non-symmetric
ion-atom absorption processes considered here, are significant not only for
quiet Sun modeling but also for sunspots and should be included {\it ab initio}
in both cases.Comment: accepted in Advances in Space Researc
- …