Atomic data from the IRON Project. LI. Electron impact excitation of Fe IX

We calculate collision strengths and thermally averaged collision strengths for electron excitation between the one hundred and forty energetically lowest levels of Fe⁸⁺. The scattering target is more elaborate than in any earlier work and large increases are found in the excitation rates among the levels of the 3s²3p⁵3d electron configuration due to resonance series that have not been considered previously. The implications for solar and stellar spectroscopy have been discussed elsewhere (Storey & Zeippen \cite{sz01}). We correct some errors that were made in generating the figures given in that paper and present corrected versions. Detailed tables of the present data are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp 130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/394/753