The shape and broadening of He lines affects radiative transport in dense, He-rich, stellar atmospheres. At wavelengths inaccessible for direct observation, we rely on theoretical calculations of ...self-broadening to support stellar structure and spectral modeling. In this work, we examine lines of He due to 1s–2p and 2p–3s transitions. The line profiles are analyzed in terms of a unified theory of spectral line broadening using ab initio potential energies that have been recently determined. For temperatures up to 20 000 K, the linear dependence of width and shift on gas density and the non-linear dependence on temperature of the Lorentzian core of the resonance line are described. Beyond the conventional symmetrical Lorentzian core, we show that they are asymmetrical and have significant additional contributions on the short wavelength side. This blue asymmetry is a consequence of maxima in the corresponding He2 potential energy difference curves at short and intermediate internuclear distance. Over a limited range of density and temperature, laboratory measurements in the visible and near infrared can be used to validate the potentials that underlie the spectral line profile theory, which is useful for modeling spectra over the extreme ranges of temperature and density encountered in stellar and planetary atmospheres.
Lithium-ion batteries have become the focus of research interest, thanks to their numerous benefits for vehicle applications. One main limitation of these technologies resides in the battery ageing. ...The effects of battery ageing limit its performance and occur throughout their whole life, whether the battery is used or not, which is a major drawback on real usage. Furthermore, degradations take place in every condition, but in different proportions as usage and external conditions interact to provoke degradations. The ageing phenomena are highly complicated to characterize due to the factors cross-dependence. This paper reviews various aspects of recent research and developments, from different fields, on lithium-ion battery ageing mechanisms and estimations. In this paper is presented a summary of techniques, models and algorithms used for battery ageing estimation (SOH, RUL), going from a detailed electrochemical approach to statistical methods based on data. In order to present the accuracy of currently used methods, their respective characteristics are discussed. Remaining challenges are deeply detailed, along with a discussion about the ideal method resulting from existing methods.
•A review of the progress made for understanding battery ageing phenomena is provided.•The ageing battery estimation methods are summarized and compared.•The challenges and unresolved issues for battery ageing estimation are discussed.
This study of the self-broadening of the 728 nm He line is performed in order to establish similarities and differences to the self-broadening of the triplet 3s-2p line at 706 nm. In a previous work ...we presented the first calculations of He-He collisional profiles at 706nm due to the triplet 3s-2p transition in a unified line shape semi-classical theory using ab-initio molecular potentials. The excellent agreement between experimental and theoretical determinations of the near wing of the line profiles established the accuracy of the interaction potentials. New ab-initio potentials for the singlet 3s-2p transitions allow us to extend our previous study to the line at 728 nm.
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