Relativistic excitation rate coefficients for Fe XXII
with inclusion of radiation damping  |
| Hong Lin Zhang and Anil K. Pradhan |
| Astronomy & Astrophysics Supplement Series, 1997, Vol.123, No.1, pp.575 |
New collision strengths
have been calculated for 990 transitions among 45 fine structure n=2 and
n=3 levels of Fe XXII.
The relativistic Breit-Pauli formulation of the R-matrix method was
employed in the close coupling approximation, with
radiation damping of autoionizing resonances included for the first time
in the calculations of excitation rate coefficients.
It is found that, at low temperatures, the relativistic effects
considerably enhance rate coefficients for the intercombination transitions,
and the radiation damping effect reduces those for a few transitions.
It is also found that
resonances due to coupling with the 
levels significantly
enhance rate coefficients for the transitions to low-lying levels
at intermediate and high temperatures, and
for the transitions to the 
high-lying levels at all temperatures.
It is expected that the new data, tabulated at a wide range of temperatures,
would lead to a revision of the spectral diagnostics of Fe XXII in
laboratory and astrophysical sources, in
particular the X-ray spectra observed from solar flares and tokamaks.