  Time dependent numerical simulations of the K ALPHA complex of Fe XXV are
carried out as a function of temperature/density/radiation field variations in
high-temperature astrophysical and laboratory plasmas. In addition to several
well known features, the transient and steady state spectra reveal the effects
due to (a) time-dependent thermal and non-thermal radiation fields, (b) photo
and collisional excitation and ionization, and (c) high densities, on the
`quartet' of principal w,x,y,z lines, and dielectronic satellites. The highly
detailed models show precisely how, assuming a temporal-temperature
correlation, the X-ray intensity varies between 6.6 - 6.7 keV and undergoes a
`spectral inversion' in the w and z line intensities, characterizing an
ionization or a recombination dominated plasma. The dielectronic satellite
intensities are the most temperature dependent features, but insensitive to
density variations, and significantly contribute to the K ALPHA complex for T <
6.7 keV leading to asymmetric profiles. The 6.7 keV K ALPHA complex should be a
potential diagnostic of X-ray flares in AGN, afterglows in gamma-ray bursts,
and other non-equilibrium sources with the high-resolution measurements
possible from the upcoming mission Astro-E2. It is also shown that high
electron densities attenuate the line intensities in simulations relevant to
laboratory plasmas, such as in inertial confinement fusion, laser, or magnetic
Z-pinch devices.
