Issue |
Astron. Astrophys. Suppl. Ser.
Volume 125, Number 3, November I 1997
|
|
---|---|---|
Page(s) | 543 - 549 | |
DOI | https://doi.org/10.1051/aas:1997241 | |
Published online | 15 November 1997 |
Effective collision strengths for electron-impact excitation of nitrogen-like Mg vi *
Department of Applied Mathematics and Theoretical Physics, The Queens University of Belfast, Belfast BT7 1NN, UK
Send offprint request to: C.A. Ramsbottom
Received:
13
January
1997
Accepted:
19
January
1997
Effective collision strengths for electron-impact excitation of the
N-sequence ion Mg vi are evaluated in the close-coupling
approximation using the multichannel R-matrix method. Twelve
LS target eigenstates are included in the expansion of the total
wavefunction, consisting of the eight states with configurations
2s22p3, 2s2p4 and 2p5, and the four
states with
configuration 2s22p23s. These 12 ionic states correspond to 23
fine-structure levels, leading to a total of 253 independent
transitions. The effective collision strengths for all possible forbidden,
semi-forbidden and allowed transitions are obtained by averaging the
electron collision strengths, for a wide range of incident electron
energies, over a Maxwellian distribution of velocities. Results are
tabulated for electron temperatures,
T, in the range log T() = 5.0
to
() = 6.1, which are the temperatures of interest for many
astrophysical applications. We conclude that the effective collision
strengths, for many of the forbidden lines considered, are significantly enhanced by
autoionizing resonances converging to the target state thresholds in the
collisional cross sections. The present calculations are the first to
include such resonance phenomena.
Key words: atomic data / atomic processes
© European Southern Observatory (ESO), 1997