Atomic data from the IRON project. LXIV. Radiative transition rates and collision strengths for Ca II
Abstract
Aims:This work reports radiative transition rates and electron impact excitation rate coefficients for levels of the n = 3, 4, 5, 6, 7, 8 configurations of Ca II.
Methods: The radiative data were computed using the ThomasFermiDirac central potential method in the frozen core approximation and includes the polarization interaction between the valence electron and the core using a model potential. This method allows for configuration interactions (CI) and relativistic effects in the BreitPauli formalism. Collision strengths in LScoupling were calculated in the close coupling approximation with the Rmatrix method. Then, fine structure collision strengths were obtained by means of the intermediatecoupling frame transformation (ICFT) method which accounts for spinorbit coupling effects.
Results: We present extensive comparisons with the most recent calculations and measurements for Ca II as well as a comparison between the core polarization results and the “unpolarized” values. We find that core polarization affects the computed lifetimes by up to 20%. Our results are in very close agreement with recent measurements for the lifetimes of metastable levels. The present collision strengths were integrated over a Maxwellian distribution of electron energies and the resulting effective collision strengths are given for a wide range of temperatures. Our effective collision strengths for the resonance transitions are within ~11% from previous values derived from experimental measurements, but disagree with later computations using the distorted wave approximation.
The atomic data from this work, including energy levels, Avalues, and effective collision strengths, is available at the CDS via anonymous ftp to cdsarc.ustrasbg.fr (130.79.128.5) or via http://cdsweb.ustrasbg.fr/cgibin/qcat?J/A+A/469/1203
 Publication:

Astronomy and Astrophysics
 Pub Date:
 July 2007
 DOI:
 10.1051/00046361:20077262
 arXiv:
 arXiv:0704.3807
 Bibcode:
 2007A&A...469.1203M
 Keywords:

 atomic data;
 atomic processes;
 line: formation;
 Astrophysics
 EPrint:
 8 pages, 4 figures. The atomic data from this work, including energy levels, Avalues, and effective collision strengths, is available in electronic form at the CDS via anonymous ftp to cdsarc.ustrasbg.fr (130.79.128.5) or via http://cdsweb.ustrasbg.fr/cgibin/qcat?J/A+A/