SCATTERING OF X-RAY-EMISSION LINES BY NEUTRAL AND MOLECULAR-HYDROGEN IN THE SOLAR ATMOSPHERE AND IN THE VICINITY OF ACTIVE GALACTIC NUCLEI AND COMPACT X-RAY SOURCES

The scattering of X-ray fluorescent lines of iron by neutral and molec ular hydrogen plays a major role in many astrophysical objects. This p rocess gives rise to characteristic distortions in the scattered-line profile, which differ appreciably from those arising from the scatteri ng by free cold electrons. An analysis of the scattered-line profile m ay provide information on the degree of ionization, helium abundance, and geometry of the scattering medium in the vicinity of active galact ic nuclei and compact X-ray sources and on the surface of flare stars and the Sun.