Issue |
Astron. Astrophys. Suppl. Ser.
Volume 136, Number 2, April II 1999
|
|
---|---|---|
Page(s) | 395 - 403 | |
DOI | https://doi.org/10.1051/aas:1999464 | |
Published online | 15 April 1999 |
Atomic data from the Iron Project*
XXXVII. Electron impact excitation collision strengths and rate coefficients for Fe VI
Department of Astronomy, The Ohio State University, Columbus, OH 43210, U.S.A.
Send offprint request to: G.-X. Chen
Received:
20
November
1999
Accepted:
14
January
1999
Collision strengths and Maxwellian-averaged rate coefficients
have been calculated for 3 160 non-vanishing
transitions among 80 fine structure levels, dominated by
configurations , and
p in Fe VI.
Collision strengths are calculated
using the R-matrix method with a 34-term
close-coupling target expansion and for electron energies up to 10
Rydbergs. Detailed comparisons of rate coefficients are presented with
the relativistic Breit-Pauli calculations using a 19-level expansion
corresponding to the first 8 LS terms dominated by the ground
configuration
. For the low-lying transitions of practical
interest there is
excellent agreement, better than 10%, among three sets of rate
coefficients calculated using the 34-term and 8-term non-relativistic
calculations and the 19-level Breit-Pauli calculation, indicating that
(i) the relativistic effects are not too significant, and (ii) the
numerical uncertainties associated with the resolution of the
extensive resonances in the collision strengths are small.
Rate coefficients are tabulated in a range of temperatures, 10
K, where Fe VI is normally abundant in radiatively photoionized
or collisionally ionized plasmas sources.
A brief discussion of the calculations and sample results are given.
The present rates for Fe VI are expected to find applications in
UV spectral diagnostics of hot stellar sources and planetary nebulae.
Key words: atomic data / white dwarfs / planetary nebulae
© European Southern Observatory (ESO), 1999