EDP Sciences
Free access
Volume 444, Number 1, December II 2005
Page(s) 305 - 317
Section Atomic, molecular and nuclear data
DOI http://dx.doi.org/10.1051/0004-6361:20053290

A&A 444, 305-317 (2005)
DOI: 10.1051/0004-6361:20053290

Atomic data and spectral line intensities for Ca XIII

E. Landi1 and A. K. Bhatia2

1  Artep, Inc, Ellicott City, MD 21042, USA and Naval Research Laboratory, Washington DC, 20375-5320, USA
    e-mail: landi@poppeo.nrl.navy.mil
2  NASA/Goddard Space Flight Center Greenbelt, Maryland 20771 USA

(Received 22 April 2005 / Accepted 16 August 2005 )

Electron impact collision strengths, energy levels, oscillator strengths and spontaneous radiative decay rates are calculated for Ca XIII. The configurations used are $\rm {2s^2} \rm {2p^4}, \rm {2s2p^5}, \rm {2p^6}, \rm {2s^2} \rm {2s^{3} 3s}, \rm {2s^2} \rm {2p^{3} 3p} \, and \, \rm {2s^2}\rm {2p^{3} 3d}$ giving rise to 86 fine-structure levels in intermediate coupling. Collision strengths are calculated at five incident energies (40, 80, 120, 160 and 200 Ry) in the distorted wave approximation. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates, statistical equilibrium equations for level populations are solved at electron densities covering the range of 108-1014 cm-3 at an electron temperature of $\log T_{\rm e}({\rm K})=6.5$, corresponding to maximum abundance of Ca XIII. Relative and absolute spectral line intensities are calculated, and their diagnostic relevance is discussed. This dataset will be made available in the next version of the CHIANTI database.

Key words: atomic data -- Sun: corona -- Sun: UV radiation

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