Topics in astrophysical x-ray and gamma ray spectroscopy
A number of topics have been investigated relating to astrophysical observations that have already been made or are currently planned of spectral features, mostly emission lines, in the x-ray and gamma ray regions of the electromagnetic spectrum. These topics include: the production of characteristic x-ray and gamma ray lines by non-thermal ions, spectral features induced by processes occurring in strong magnetic fields, and the positron annihilation line at 0.5 MeV. Although astrophysical spectroscopy in this regime is quite young, a number of conclusions can be drawn from existing observations and upper limits, and much can be learned from experiments currently under consideration. First, the rate of x-ray production at 6.8 keV by the 2p to 1s transition in fast hydrogen- and helium-like iron ions was calculated, following both electron capture to excited levels and collisional excitation. A refinement of the OBK approximation was used to obtain an improved charge exchange cross section. This and the corresponding ionization cross section were used to determine the equilibrium charge fractions for iron ions as a function of their energy. The effective x-ray line production cross section was found to be sharply peaked in energy at about 10 MeV/amu. The intense magnetic fields (of order 10/sup 12/ Gauss) believed to exist at the surfaces of x-ray pulsars could produce observable structure in their spectra. Such fields severely quantize the motion of electrons in the transverse plane, and line emission and absorption can occur accompanying transitions between levels. A previous calculation of the rates for these processes was confirmed; and the cross section for electron-ion Coulomb collisions in strong fields was calculated.
- Research Organization:
- Maryland Univ., College Park (USA)
- OSTI ID:
- 6127976
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
COSMIC POSITRONS
GAMMA SPECTROSCOPY
X-RAY SPECTROSCOPY
PULSARS
RADIO GALAXIES
ANNIHILATION
COLLISIONS
CROSS SECTIONS
EMISSION SPECTRA
EMISSIVITY
ENERGY-LEVEL TRANSITIONS
EXCITATION
H2 REGIONS
INTERSTELLAR GRAINS
IRON IONS
LIMITING VALUES
MAGNETIC FIELDS
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BASIC INTERACTIONS
CHARGED PARTICLES
COSMIC RADIATION
COSMIC RADIO SOURCES
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
FERMIONS
GALAXIES
INTERACTIONS
IONIZING RADIATIONS
IONS
LEPTONS
OPTICAL PROPERTIES
PARTICLES
PHYSICAL PROPERTIES
POSITRONS
RADIATIONS
SPECTRA
SPECTROSCOPY
SURFACE PROPERTIES
640103* - Astrophysics & Cosmology- Quasi-Stellar
Radio
& X-Ray Sources- (-1987)