Exact bound–bound Gaunt factor values for quantum levels up to n = 2000

Morabito, L. K.; Harten, Gerard van; Salgado, Francisco; Oonk, J. B. R.; Röttgering, H. J. A.; Tielens, A. G. G. M.

doi:10.1093/mnras/stu775

Cited by 4 publications

(3 citation statements)

References 28 publications

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“…In order to connect the n-resolved levels, we used hydrogenic values. As we have encountered problems with the approximations recommended by Burgess & Summers (1976), we have resorted to use the analytic expressions (see, e.g., Goldberg 1935) for the gf values and the Gaunt factors precalculated with very good accuracy by Morabito et al (2014). The A values were then calculated using the energies derived from the quantum defects.…”

Section: He a Valuesmentioning

confidence: 99%

Helium Line Emissivities in the Solar Corona

Zanna

Storey

Badnell

et al. 2020

ApJ

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We present new collisional-radiative models (CRMs) for helium in the quiescent solar corona and predict the emissivities of the He and He + lines to be observed by DKIST, Solar Orbiter, and Proba-3. We discuss in detail the rates we selected for these models, highlighting several shortcomings we have found in previous work. As no previous complete and self-consistent coronal CRM for helium existed, we have benchmarked our largest model at a density of 10 6 cm −3 and temperature of 20,000 K against recent CRMs developed for photoionized nebulae. We then present results for the outer solar corona, using new dielectronic recombination rates we have calculated, which increase the abundance of neutral helium by about a factor of 2. We also find that all optical triplet He I lines, and in particular the well-known He I 10830 and 5876 Å lines, are strongly affected by both photoexcitation and photoionization from the disk radiation and that extensive CRMs are required to obtain correct estimates. Close to the Sun, at an electron density of 10 8 cm −3 and temperature of 1 MK, we predict the emissivity of He I 10830 Å to be comparable to that of the strong Fe XIII coronal line at 10798 Å. However, we expect the He I emissivity to sharply fall in the outer corona, with respect to Fe XIII. We confirm that the He + Lyα at 304 Å is also significantly affected by photoexcitation and is expected to be detectable as a strong coronal line up to several solar radii.

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Section: He a Valuesmentioning

confidence: 99%

Helium Line Emissivities in the Solar Corona

Zanna

Storey

Badnell

et al. 2020

ApJ

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“…As we have encountered problems with the approximations recommended by Burgess & Summers (1976), we have resorted to use the analytic expressions (see e.g. Goldberg 1935) for the gf values and the Gaunt factors pre-calculated with very good accuracy by Morabito et al (2014). The A-values were then calculated using the energies derived from the quantum defects.…”

Section: He A-valuesmentioning

confidence: 99%

Helium line emissivities in the solar corona

Del Zanna,

Storey,

Badnell

et al. 2020

Preprint

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We present new collisional-radiative models (CRMs) for helium in the quiescent solar corona, and predict the emissivities of the He and He + lines to be observed by DKIST, Solar Orbiter, and Proba-3. We discuss in detail the rates we selected for these models, highlighting several shortcomings we have found in previous work. As no previous complete and self-consistent coronal CRM for helium existed, we have benchmarked our largest model at a density of 10 6 cm −3 and temperature of 20,000 K against recent CRMs developed for photoionised nebulae. We then present results for the outer solar corona, using new dielectronic recombination rates we have calculated, which increase the abundance of neutral helium by about a factor of two. We also find that all the optical triplet He I lines, and in particular the well known He I 10830 and 5876 Å lines are strongly affected by both photo-excitation and photo-ionisation from the disk radiation, and that extensive CRM models are required to obtain correct estimates. Close to the Sun, at an electron density of 10 8 cm −3 and temperature of 1 MK, we predict the emissivity of the He I 10830 Å to be comparable to that of the strong Fe XIII coronal line at 10798 Å. However, we expect the He I emissivity to sharply fall in the outer corona, with respect to Fe XIII. We confirm that the He + Lyman α at 304 Å is also significantly affected by photo-excitation and is expected to be detectable as a strong coronal line up to several solar radii.

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“…Moreover, close to the limit λ th , both below and above it, numerical evaluation at finite precision of the Einstein B coefficients is troublesome (see e.g. Morabito et al 2014). For simplicity, in the present work, we explicitly compute the Einstein B coefficients inside a safe range (for 1000 boundbound transitions and 300 bound-free transitions) and interpolate its values for transitions closer to the limit.…”

Section: Numerical Modelling Of the Total Cross-section Around The Bamentioning

confidence: 99%

Structure of the Balmer jump

Calvo

Belluzzi

Steiner

2018

A&A

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Context. The spectrum of the hydrogen atom was explained by Bohr more than one century ago. We revisit here some of the aspects of the underlying quantum structure, with a modern formalism, focusing on the limit of the Balmer series. Aims. We investigate the behaviour of the absorption coefficient of the isolated hydrogen atom in the neighbourhood of the Balmer limit. Methods. We analytically computed the total cross-section arising from bound-bound and bound-free transitions in the isolated hydrogen atom at the Balmer limit, and established a simplified semi-analytical model for the surroundings of that limit. We worked within the framework of the formalism of Landi Degl’Innocenti & Landolfi (2004, Astrophys. Space Sci. Lib., 307), which permits an almost straight-forward generalization of our results to other atoms and molecules, and which is perfectly suitable for including polarization phenomena in the problem. Results. We analytically show that there is no discontinuity at the Balmer limit, even though the concept of a “Balmer jump” is still meaningful. Furthermore, we give a possible definition of the location of the Balmer jump, and we check that this location is dependent on the broadening mechanisms. At the Balmer limit, we compute the cross-section in a fully analytical way. Conclusions. The Balmer jump is produced by a rapid drop of the total Balmer cross-section, yet this variation is smooth and continuous when both bound-bound and bound-free processes are taken into account, and its shape and location is dependent on the broadening mechanisms.

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Exact bound–bound Gaunt factor values for quantum levels up to n = 2000

Cited by 4 publications

References 28 publications

Helium Line Emissivities in the Solar Corona

Helium Line Emissivities in the Solar Corona

Helium line emissivities in the solar corona

Structure of the Balmer jump

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