Systematic Studies of N IV Transitions of Astrophysical Importance

Fleming, Janine; Brage, Tomas; Bell, K. R.; Vaeck, Nathalie; HIibbert, A; Godefroid, Michel; Fischer, Charlotte Froese

doi:10.1086/176621

Cited by 41 publications

(53 citation statements)

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“…The experimental data are also presented [2,3]. The values from this work are in a very good coincidence with the results presented in [6] for all the transitions 2p 2 3 P J2s2p 3 P J , therefore they are only partially presented in the table. As seen from the table, the results of this work agree well with the CIV3, MCHF, MCDF, and the experimental data.…”

Section: Discussion Of the Resultssupporting

confidence: 86%

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Comparison of two theoretical methods for studying 2-2 transitions in beryllium isoelectronic sequence

Bogdanovich¹

2007

Lithuanian J. Phys.

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Theoretical investigation of characteristics of allowed dipole 2-2 transitions in beryllium isoelectronic sequence is performed applying two different theoretical methods: the relativistic many-body perturbation theory and the configuration interaction method. The data on oscillator strengths are obtained for ions with nucleus charge ranging from 4 till 29. The calculated data reveal a very good coincidence of these two methods almost for all investigated ions. The comparison of results of the present work with experimental and theoretical data of other authors for N III and Fe XXIII shows that the level of accuracy of the obtained oscillator strength values is high enough for interpretation of the experimental data as well as for modelling of the different types of plasma.

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Section: Discussion Of the Resultssupporting

confidence: 86%

“…Numerous publications devoted to investigations of both the energy spectra and the transition characteristics confirm this. The data for the particular ions are presented in papers [1][2][3][4][5][6][7][8][9][10][11][12] and references therein. The aim of the present work is to investigate the allowed 2-2 transitions in the long (Z = 4, .…”

Section: Introductionmentioning

confidence: 99%

Comparison of two theoretical methods for studying 2-2 transitions in beryllium isoelectronic sequence

Bogdanovich¹

2007

Lithuanian J. Phys.

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“…Similarly, for the 2s 2 1 S -2s2p 3 P 1 intercombination transition, the experimental A-value of Doerfert et al (1997) was used. For forbidden transitions we have employed the calculations of Jönsson et al (1998) and Fleming et al (1996). Proton excitation rates, which will only be important for transitions within 2s2p 3 P (Seaton 1964), were obtained from Ryans et al (1998).…”

Section: Methodsmentioning

confidence: 99%

Opacity in the upper atmosphere of AU Mic

Bloomfield

Mathioudakis

Christian

et al. 2002

A&A

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Abstract. In this paper we investigate the validity of the optically thin assumption in the transition region of the late-type star AU Mic. We use Far-Ultraviolet Spectroscopic Explorer (FUSE) observations of the C  multiplet and O  resonance lines, hence yielding information at two different levels within the atmosphere. Significant deviations from the optically thin fluxes are found for C  in both quiescent and flare spectra, where only 60% of the flux is actually observed. This could explain the apparent deviation of C  observed in emission measure distributions. We utilize escape probabilities for both homogeneous and inhomogeneous geometries and calculate optical depths as high as 10 for the C  1175.71 Å component of the multiplet. Using a lower limit to the electron density (10 11 cm −3 ) we derive an effective thickness of <100 km for the scattering layer. The emission originates from very small and compact regions, consistent with a filling factor of 10 −5 derived for the flare plasma.

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“…We also display in Table 1 some later calculations of Fleming et al [3][4][5]. They used the Breit-Pauli versions of the the general configuration interaction code CIV3 [8] and the MCHF (Multi-Configurational Hartree-Fock) code [9] and found that, with a larger number of correlation configurations, and in both the valence and core shells, the length and velocity forms show excellent agreement.…”

Section: The Inadequacy Of Very Simple Calculationsmentioning

confidence: 88%

“…During our studies of these transitions, it became apparent that while the upper levels did exhibit strong configuration mixing, a third main component, corresponding to the 3d 6 5p 4 F o configuration, also interacted strongly. It also became apparent that it was the size of the component of 4p 4 G o in the wave function of each of the three levels that determined the size of the oscillator strengths of the transitions. It can be seen in Table 5 that our fine-tuning process, following on from an already extensive ab initio calculation, resulted in the two upper levels of these lines having almost equal components of the 4 G o configuration, resulting in our two calculated oscillator strengths being almost equal.…”

Section: The 2507552 2509097 å Lines In Fe IImentioning

confidence: 99%

Successes and Difficulties in Calculating Atomic Oscillator Strengths and Transition Rates

Hibbert

2018

Galaxies

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Abstract:There is an on-going need for accurate oscillator strengths to be used in astrophysical applications, particularly in plasma diagnostics and in the modelling of stellar atmospheres and the interstellar medium. There are several databases in regular use which contain some of the required data, although often insufficiently complete, and sometimes not sufficiently accurate. In addition, several atomic structure packages are available through the literature, or from their individual authors, which would allow further calculations to be undertaken. Laboratory measurements provide an important check on the accuracy of calculated data, and the combined efforts of theorists and experimentalists have succeeded in providing data of an accuracy sufficient for some astrophysical applications. However, the insufficiency or inadequacy of atomic data is a continuing problem. We discuss in the context of appropriate examples some of the principal steps which researchers have taken to calculate accurate oscillator strengths, including both ab initio results and also various extrapolation processes which attempt to improve such results. We also present some examples of the main causes of difficulty in such calculations, particularly for complex (many-electron) ions, and indicate ways in which the difficulties might be overcome.

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Systematic Studies of N IV Transitions of Astrophysical Importance

Cited by 41 publications

References 0 publications

Comparison of two theoretical methods for studying 2-2 transitions in beryllium isoelectronic sequence

Comparison of two theoretical methods for studying 2-2 transitions in beryllium isoelectronic sequence

Opacity in the upper atmosphere of AU Mic

Successes and Difficulties in Calculating Atomic Oscillator Strengths and Transition Rates

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