Observations of the second solar spectrum (SSS) revealed the existence of prominent linear polarization signals due to lines of the C2 molecule. Interpretation of the SSS is the only tool to obtain the weak and turbulent magnetic field which is widespread in the Quiet Sun. However, this interpretation is conditioned by the determination of accurate collisional data. In this context, we present a formulation of the problem of the calculation of the polarization transfer rates by collisions of polarized C2 states with electrons. The obtained formulae are applied to determine, for the first time, the polarization transfer rates between the C2 states of the Swan band electronic system (a 3Π u – d 3Π g ) and electrons for temperatures going up from 1000 to 10 000 K. However, due to the closeness of the electronic states of the C2 molecule, the two electronic d 3Π g and a 3Π u cannot be disconnected from the other electronic levels and, thus, a model based on only two states is not sufficient to describe the formation of the lines in the Swan band. Consequently, we also calculated the collisional polarization transfer rates in the case where the first eight electronic states of C2 are taken into account. All rates are given as functions of the temperature by power laws. Our results should be useful for future solar applications.
Existence of linear polarization, formed by anisotropic scattering in the photosphere, has been demonstrated observationally as well as theoretically and is called second solar spectrum (SSS). The SSS is distinguished by its structure, which is rich in terms of information. In order to analyze the SSS, it is necessary to evaluate the (de)polarizing effect of isotropic collisions between CN solar molecules and electrons or neutral hydrogen atoms. This work is dedicated to calculations of the polarization transfer rates associated with CN–electron isotropic collisions. We show that usual rates serve as a proxy for polarization transfer rates. Then, we take advantage of available usual excitation collisional rates obtained via sophisticated quantum methods in order to derive the polarization transfer rates for the X 2Σ+– B 2Σ+ (violet) and X 2Σ+–A 2Π (red) systems of CN. Our approach is based on the infinite order sudden (IOS) approximation and can be applied for other solar molecules. We discuss the effectiveness of collisions with electrons on the SSS of the CN lines. Our results contribute to reducing the degree of complication in modeling the formation of the SSS of CN.
We are interested in quantum calculations of polarization transfer (PT) rates due to collisions of the SiO molecule with the electrons. We determine the inelastic PT rates associated to the transitions: X 1Σ+→3Π; X 1Σ+→3Σ+; X 1Σ+→3Δ; X 1Σ+→3Σ−. In addition, we calculate the elastic PT rates due to rotational transitions inside the electronic state X 1Σ+ which are related to observed astronomical SiO MASERs. Our PT rates are obtained through linear combination of excitation rates previously calculated for SiO-electron collisions. The calculations are performed on a collision energy grid large enough to ensure converged state-to-state rates for temperatures ranging from 1000 to 10,000 K for inelastic rates and from 5 to 5000 K for elastic rates. The dependence of the inelastic rates on temperatures is obtained analytically and given in useful form.
In solar and stellar atmospheres, atomic excitation by impact with electrons plays an important role in the formation of spectral lines. We make use of available experimental and theoretical cross-sections to calculate the excitation rates in s–p transitions of alkali and alkaline atoms through collisions with electrons. Then, we infer a general formula for calculating the excitation rates by using genetic programming numerical methods. We propose an extension of our approach to deduce collisional excitation rates for complex atoms and atoms with hyperfine structure. Furthermore, the developed method is also applied to determine collisional polarization transfer rates. Our results are not specific to a given atom and can be applied to any s–p atomic transition. The accuracy of our results is discussed.
Scattering of anisotropic radiation by atoms, ions or molecules is sufficient to generate linear polarization observable in stars’ and planets’ atmospheres, circumstellar environments, and in particular in the Sun’s atmosphere. This kind of polarization is called scattering polarization (SP) or second solar spectrum (SSS) if it is formed near the limb of the solar photosphere. Generation of linear SP can typically be reached more easily than circular SP. Interestingly, the latter is often absent in observations and theories. Intrigued by this, we propose to demonstrate how circular SP can be created by anisotropic collisions if a magnetic field is present. We also demonstrate how anisotropic collisions can result in the creation of circular SP if the radiation field is anisotropic. We show that under certain conditions, linear SP creation is accompanied by the emergence of circular SP which can be useful for diagnostics of solar and astrophysical plasmas. We treat an example and calculate the density matrix elements of tensorial order k = 1 which are directly associated with the presence of circular SP. This work should encourage theoretical and observational research to be increasingly oriented towards circular SP profiles in addition to linear SP in order to improve our analysis tools of astrophysical and solar observations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.