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G. V. Brown, P. Beiersdorfer, D. A. Liedahl, S. B. Utter, K. Widmann, V. Decaux (Lawrence Livermore National Laboratory)
Owing to its presence in a multitude of sources including stellar coronae, supernova remnants, and active galactic nuclei, its distinct spectral features, and strong emission over a broad temperature range, the L--shell transitions in Fe XVII--XXIV, falling in the 11--18 Å\space range, have been studied by several authors with the prospect of extracting their full diagnostic potential. The diagnostic power of the L--shell spectra relies heavily on spectral modeling packages to make accurate fits to the data. In order to increase both the accuracy and the completeness of the databases on which these modeling packages rely, we have identified and measured the wavelengths of all the pertinent L--shell transitions from Fe XVIII--XXIV from 11 to 17.7 Å. Our results include nearly 200 wavelengths and identifications from levels originating in n = 3 or 4. Addition of preliminary Fe L--shell wavelength data to the MEKAL spectral modeling package database has already lead to improvements of approximately a factor of three to the \chi2 of fits to solar spectra obtained by the Solar Maximum Mission. This improvement further demonstrates the need for a more accurate and complete set of atomic data necessary to fit higher resolution data such as will be available after the launch of the Chandra X--Ray Observatory and the X--Ray Multi--Mirror Mission later this year.
This work was performed under the auspices of the U.S.D.o.E. under Contract No. W-7405-Eng-48 and supported by NASA HEA X-ray Astronomy Research and Analysis grant NAG5-5123 and work order W-19127.
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