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   PR # 12205
    Fe L-shell emission has recently been observed in X-ray spectra of
    several AGN,including both Sy 1s and 2s. These lines providesensitive
    diagnostics of physical conditions in such systems,primarily through
    considerations of the thermal stability ofthe emitting gas. The detai
    led spectral structure is not well described by standard spectral syn
    thesis models,because the lines are formed through recombination cas-
    cades, as opposed to collisional excitation. We propose ASCA observat
    ions of Mkn509 and NGC 2992, for which iron L complexes have already
    been detected with the Einstein SSS. Our primary goal is to unambiguo
    usly determine the emission measure distribution as a function of cha
    rge state, which can then be used to constrain the structure of the c
   ircum source environment.
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