Electron-Ion Recombination Rate Coefficients, Photoionization Cross Sections, and Ionization Fractions for Astrophysically Abundant Elements. II. Oxygen Ions

We present a comprehensive and self-consistent set of new atomic data for ionization balance in radi- atively and collisionally ionized astrophysical plasmas. Complex resonant phenomena resulting in rapid energy variation in the cross sections for photoionization and recombination require accurate and large- scale calculations, as reported. Another new development is the consideration of the uni-ed nature of the recombination process in an ab initio manner, via resonances embedded in the electron-ion continua, which have been heretofore considered as separate processes of radiative recombination and dielectronic recombination. A single set of total electron-ion recombination rate coefficients is thereby obtained as a function of electron temperature. The present calculations also meet the hitherto neglected, but theoreti- cally essential, criterion of self-consistency between the rates for the inverse processes of photoionization and recombination, ensured by describing all atomic processes with an identical set of eigenfunction expansion within the close-coupling approximation using the R-matrix method. Photoionization cross sections and total electron-ion recombination rate coefficients for the carbon and nitrogen isonuclear sequences, C IEC VI and N IEN VII, are presented. Ionization fractions in coronal equilibrium are also computed. The present photoionization cross sections have been calculated using more extensive eigen- function expansions than those in the Opacity Project. In addition to the total photoionization and recombination data, state-speci-c cross sections are also obtained for a large number of excited states for non-LTE models. Complete data sets are available electronically. Subject headings: atomic data E atomic processes E plasmas

[1]  K A Berrington,et al.  Atomic data for opacity calculations. XIV. The beryllium sequence , 1990 .

[2]  H. E. Saraph,et al.  Atomic data for opacity calculations. IX. The lithium isoelectronic sequence , 1988 .

[3]  M. Seaton,et al.  Dielectronic recombination. I. General theory , 1985 .

[4]  W. Eissner,et al.  Techniques for the calculation of atomic structures and radiative data including relativistic corrections , 1974 .

[5]  N. Badnell.  The influence of core fine-structure interactions on dielectronic recombination at low temperatures: B-like C, N and O recombined ions , 1988 .

[6]  F. J. Smith,et al.  Recommended Data on the Electron Impact Ionization of Atoms and Ions: Fluorine to Nickel , 1988 .

[7]  A. Hibbert,et al.  Photoionization of ground-state nitrogen atoms , 1976 .

[8]  Pradhan,et al.  Unified treatment of electron-ion recombination in the close-coupling approximation. , 1994, Physical review. A, Atomic, molecular, and optical physics.

[9]  A. Pradhan,et al.  Atomic data for opacity calculations. XI. The carbon isoelectronic sequence , 1989 .

[10]  D. G. Hummer,et al.  Fast computer evaluation of radiative properties of hydrogenic systems , 1991 .

[11]  Badnell,et al.  Intermediate-coupling effects in the dielectronic recombination of oxygen ions. , 1989, Physical review. A, General physics.

[12]  Sultana N. Nahar,et al.  Total electron-ion recombination of Fe III , 1996 .

[13]  Norman Scott,et al.  A general program to calculate atomic continuum processes incorporating model potentials and the Breit-Pauli Hamiltonian within the R-matrix method , 1984 .

[14]  S. Nahar.  Photoionization cross sections and oscillator strengths for oxygen ions: O I-O VII , 1998 .

[15]  S. Younger.  Electron ionization rate coefficient for highly ionized iron and scandium , 1983 .

[16]  S. Nahar.  Electron-Ion Recombination Rate Coefficients For Si I, Si II, S II, S III, C II, and C-like Ions C I, N II, O III, F IV, Ne V, Na VI, Mg VII, Al VIII, Si IX, and S XI , 1995 .

[17]  S. Younger.  Electron impact ionization rate coefficients and cross sections for highly ionized iron. , 1982 .

[18]  J. Shull,et al.  The ionization equilibrium of astrophysically abundant elements , 1982 .

[19]  M. Seaton,et al.  Opacities for stellar envelopes , 1994 .

[20]  H. L. Zhang,et al.  Radiation damping of autoionizing resonances , 1997 .

[21]  S. Younger.  Electron impact ionization cross sections and rates for highly ionized atoms. , 1981 .

[22]  V. Jacobs,et al.  The influence of autoionization accompanied by excitation on dielectronic recombination and ionization equilibrium. [in high temperature astrophysical plasmas] , 1977 .

[23]  Griffin,et al.  Dielectronic recombination from the ground and excited states of C4+ and O6+ , 1990, Physical review. A, Atomic, molecular, and optical physics.

[24]  F. J. Smith,et al.  Recommended Data on the Electron Impact Ionization of Light Atoms and Ions , 1983 .

[25]  P G Burke,et al.  Atomic data for opacity calculations. II. Computational methods , 1987 .

[26]  Photoionization and electron-ion recombination: The carbon sequence. , 1991, Physical review. A, Atomic, molecular, and optical physics.

[27]  S. Nahar,et al.  Unified Electron-Ion Recombination Rate Coefficients of Silicon and Sulfur Ions , 1995 .

[28]  Manuel A. Bautista,et al.  Electron-Ion Recombination of Neutral Iron , 1997 .

[29]  M. Dopita,et al.  Cooling functions for low-density astrophysical plasmas , 1993 .

[30]  D. Osterbrock,et al.  Astrophysics of Gaseous Nebulae and Active Galactic Nuclei , 1989 .

[31]  M. Seaton,et al.  Atomic data for opacity calculations. IV. Photoionisation cross sections for C II , 1987 .

[32]  C. Zeippen,et al.  The photoionisation of the 4S0 ground state of atomic nitrogen , 1979 .

[33]  H. L. Zhang,et al.  Photorecombination Spectra of Highly Charged Ions , 1997 .

[34]  V. Jacobs,et al.  Ionization equilibrium and radiative energy loss rates for C, N, and O ions in low-density plasmas. Interim report , 1977 .

[35]  Samson,et al.  Single- and double-photoionization cross sections of atomic nitrogen from threshold to 31. , 1990, Physical review. A, Atomic, molecular, and optical physics.

[36]  N. Badnell.  Dielectronic recombination rate coefficients for Be-like ions: Z=6-42 , 1987 .

[37]  A. Burgess.  A General Formula for the Estimation of Dielectronic Recombination Co-Efficients in Low-Density Plasmas. , 1965 .

[38]  M. Seaton,et al.  Atomic data for opacity calculations. I. General description , 1987 .

[39]  M. Seaton,et al.  Atomic data for opacity calculations. VII. Energy levels, f values and photoionisation cross sections for He-like ions , 1987 .

[40]  S. Manson,et al.  Photoabsorption cross sections for positive atomic ions with Z equal to or less than 30 , 1979 .