Highly excited core resonances in photoionization of Fe xvii: Implications for plasma opacities

Journal Article · Sun May 15 00:00:00 EDT 2011 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.83.053417· OSTI ID:21546800

Nahar, Sultana N; Pradhan, Anil K ^[1]; Guoxin, Chen ^[2]; Eissner, Werner ^[3]

---

1. Department of Astronomy, The Ohio State University, Columbus, Ohio 43210 (United States)
2. ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)
3. Institut fuer Theoretische Physik, Teilinstitut 1, D-70550 Stuttgart (Germany)

A comprehensive study of high-accuracy photoionization cross sections is carried out using the relativistic Breit-Pauli R-matrix (BPRM) method for (h{nu}+Fe xvii {yields} Fe xviii +e). Owing to its importance in high-temperature plasmas, the calculations cover a large energy range, particularly the myriad photoexcitation-of-core (PEC) resonances including the n=3 levels not heretofore considered. The calculations employ a close-coupling wave-function expansion of 60 levels of the core ion Fe xviii ranging over a wide energy range of nearly 900 eV between the n=2 and n=3 levels. Strong-coupling effects due to dipole transition arrays 2p{sup 5}{yields}2p{sup 4}(3s,3d) manifest themselves as large PEC resonances throughout this range and enhance the effective photoionization cross sections orders of magnitude above the background. Comparisons with the erstwhile Opacity Project (OP) and other previous calculations show that the currently available cross sections considerably underestimate the bound-free cross sections. A level-identification scheme is used for spectroscopic designation of the 454 bound fine structure levels of Fe xvii, with n{<=}10, l{<=}9, and 0{<=}J{<=}8 of even and odd parities, obtained using the ab initio BPRM method (compared to 181 LS bound states in the OP work). The calculated energies are compared with those available from the National Institute for Standards and Technology database, which lists 63 levels with very good agreement. Level-specific photoionization cross sections are computed for all levels. In addition, partial cross sections for leaving the core ion Fe xvii in the ground state are also obtained. These results should be relevant to modeling of astrophysical and laboratory plasma sources requiring (i) photoionization rates, (ii) extensive nonlocal-thermodynamic-equilibrium models, (iii) total unified electron-ion recombination rates including radiative and dielectronic recombination, and (iv) plasma opacities. We particularly examine PEC and non-PEC resonance strengths and emphasize their expanded role to incorporate inner-shell excitations for improved opacities, as shown by the computed monochromatic opacity of Fe xvii.

• OSTI ID: 21546800
• Journal Information: Physical Review. A, Vol. 83, Issue 5; Other Information: DOI: 10.1103/PhysRevA.83.053417; (c) 2011 American Institute of Physics; ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ACCURACY
COMPARATIVE EVALUATIONS
CROSS SECTIONS
DIPOLES
ELECTRON-ION COLLISIONS
EV RANGE
FINE STRUCTURE
HOT PLASMA
INNER-SHELL EXCITATION
IRON IONS
MONOCHROMATIC RADIATION
PARITY
PHOTOIONIZATION
R MATRIX
RECOMBINATION
RELATIVISTIC RANGE
RESONANCE
STRONG-COUPLING MODEL
WAVE FUNCTIONS
CHARGED PARTICLES
COLLISIONS
ELECTROMAGNETIC RADIATION
ELECTRON COLLISIONS
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EVALUATION
EXCITATION
FUNCTIONS
ION COLLISIONS
IONIZATION
IONS
MATHEMATICAL MODELS
MATRICES
MULTIPOLES
PARTICLE MODELS
PARTICLE PROPERTIES
PLASMA
RADIATIONS