skip to main content

SciTech ConnectSciTech Connect

Title: A comprehensive X-ray absorption model for atomic oxygen

An analytical formula is developed to accurately represent the photoabsorption cross section of O I for all energies of interest in X-ray spectral modeling. In the vicinity of the K edge, a Rydberg series expression is used to fit R-matrix results, including important orbital relaxation effects, that accurately predict the absorption oscillator strengths below threshold and merge consistently and continuously to the above-threshold cross section. Further, minor adjustments are made to the threshold energies in order to reliably align the atomic Rydberg resonances after consideration of both experimental and observed line positions. At energies far below or above the K-edge region, the formulation is based on both outer- and inner-shell direct photoionization, including significant shake-up and shake-off processes that result in photoionization-excitation and double-photoionization contributions to the total cross section. The ultimate purpose for developing a definitive model for oxygen absorption is to resolve standing discrepancies between the astronomically observed and laboratory-measured line positions, and between the inferred atomic and molecular oxygen abundances in the interstellar medium from XSTAR and SPEX spectral models.
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ; ; ;  [5] ;  [6] ;  [7] ;  [8]
  1. Department of Physics, Western Michigan University, Kalamazoo, MI 49008 (United States)
  2. Hasan Kalyoncu University, 27100 Sahinbey, Gaziantep (Turkey)
  3. Harvard-Smithsonian Center for Astrophysics, MS-6, 60 Garden Street, Cambridge, MA 02138 (United States)
  4. Centro de Física, Instituto Venezolano de Investigaciones Científicas, Caracas 1020 (Venezuela, Bolivarian Republic of)
  5. SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584-CA Utrecht (Netherlands)
  6. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  7. Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 (United States)
  8. Department of Physics and Astronomy, Drake University, Des Moines, IA 50311 (United States)
Publication Date:
OSTI Identifier:
22348498
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 779; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ABUNDANCE; ATOMS; COMPUTERIZED SIMULATION; LINEAR ABSORPTION MODELS; OSCILLATOR STRENGTHS; OXYGEN; PHOTOIONIZATION; R MATRIX; RELAXATION; RYDBERG STATES; THRESHOLD ENERGY; TOTAL CROSS SECTIONS; X RADIATION