CHIANTI-AN ATOMIC DATABASE FOR EMISSION LINES. XI. EXTREME-ULTRAVIOLET EMISSION LINES OF Fe VII, Fe VIII, AND Fe IX OBSERVED BY HINODE/EIS

A detailed study of emission lines from Fe VII, Fe VIII, and Fe IX observed by the EUV Imaging Spectrometer on board the Hinode satellite is presented. Spectra in the ranges 170-212 angstrom and 246-292 angstrom show strongly enhanced lines from the upper solar transition region (temperatures 5.4 <= log T <= 5.9) allowing a number of new line identifications to be made. Comparisons of Fe VII lines with predictions from a new atomic model reveal new plasma diagnostics, however there are a number of disagreements between theory and observation for emission line ratios insensitive to density and temperature, suggesting improved atomic data are required. Line ratios for Fe VIII also show discrepancies with theory, with the strong lambda 185.21 and lambda 186.60 lines underestimated by 60%-80% compared to lines between 192 and 198 angstrom. A newly identified multiplet between 253.9 and 255.8 angstrom offers excellent temperature diagnostic opportunities relative to the lines between 185 and 198 angstrom, however the atomic model underestimates the strength of these lines by factors of 3-6. Two new line identifications are made for Fe IX at wavelengths 176.959 angstrom and 177.594 angstrom, while seven other lines between 186 and 200 angstrom are suggested to be due to Fe IX but for which transition identifications cannot be made. The new atomic data for Fe VII and Fe IX are demonstrated to significantly modify models for the response function of the Transition Region And Coronal Explorer 195 angstrom imaging channel, affecting temperature determinations from this channel. The data will also affect the response functions for other solar EUV imaging instruments such as SOHO/EIT, STEREO/EUVI, and the upcoming AIA instrument on the Solar Dynamics Observatory.