Physics – Atomic Physics
Scientific paper
Jan 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt........77l&link_type=abstract
PhD Dissertation, California Univ. Berkeley, CA United States
Physics
Atomic Physics
8
Plasma Radiation, Photoionization, Emission Spectra, Line Spectra, X Ray Spectra, Spectrum Analysis, Atomic Physics, Plasma Diagnostics, Ferric Ions
Scientific paper
Plasma emission codes have become a standard tool for the analysis of spectroscopic data from cosmic X-ray sources. However, the assumption of collisional equilibrium, typically invoked in these codes, renders them inapplicable to many important astrophysical situations, particularly those involving X-ray photoionized nebulae, which are likely to exist in the circumsource environments of compact X-ray sources. X-ray line production in a photoionized plasma is primarily the result of radiative cascades following recombination. Through the development of atomic models of several highly-charged ions, this work extends the range of applicability of discrete spectral models to plasmas dominated by recombination. Assuming that ambient plasma conditions lie in the temperature range 105-106 K and the density range 1011-1016 cm-3, X-ray line spectra are calculated over the wavelength range 5-45 A using the HULLAC atomic physics package. Several new plasma diagnostics are identified. The accumulated atomic data are being prepared for incorporation into spectral models, analogous to coronal plasma emission codes . Most of the work focuses on the Fe L-shell ions. Line ratios of the form (3s-2p)/(3d-2p) are shown to characterize the principal mode of line excitation, thereby providing a simple signature of photoionization. At electron densities exceeding 1012 cm-3, metastable state populations in the ground configurations approach their LTE value, resulting in the enrichment of the Fe L-shell recombination spectrum and a set of density-sensitive X-ray line ratios. Radiative recombination continua and emission lines produced selectively by (Delta)n = 0 dielectronic recombination are shown to provide two classes of temperature diagnostics. Because of the extreme over ionization, the recombination continua are expected to be narrow ((Delta)E/E much less than 1), with (Delta)E = kT. Dielectronic recombination selectively drives radiative transitions that originate on states with vacancies in the 2s subshell, states that are inaccessible under pure RR population kinetics. Since these two recombination processes have different temperature dependences, the intensity ratio of a DR-driven line to a RR-driven line is temperature sensitive.
No associations
LandOfFree
X-ray emission lines from photoionized plasmas does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with X-ray emission lines from photoionized plasmas, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and X-ray emission lines from photoionized plasmas will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-939921