  Four Fe IX transitions in the wavelength range 188--198 A are identified for
the first time in spectra from the EUV Imaging Spectrometer on board the Hinode
satellite. In particular the emission line at 197.86 A is unblended and close
to the peak of the EIS sensitivity curve, making it a valuable diagnostic of
plasma at around 800,000 K - a critical temperature for studying the interface
between the corona and transition region. Theoretical ratios amongst the four
lines predicted from the CHIANTI database reveal weak sensitivity to density
and temperature with observed values consistent with theory. The ratio of
197.86 relative to the 171.07 resonance line of Fe IX is found to be an
excellent temperature diagnostic, independent of density, and the derived
temperature in the analysed data set is log T=5.95, close to the predicted
temperature of maximum ionization of Fe IX.
