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For crucial tests between theory and experiment, ab initio close coupling calculations are carried out for photoionization of O II, O III, O IV, O V. The relativistic fine structure and resonance effects are studied using the R-matrix and…

Astrophysics · Physics 2009-11-10 Sultana N. Nahar

Photoionization cross sections and recombination rate coefficients are presented for the L-shell ground state fine structure levels $2s^22p^4 \ ^3P_{2,0,1}$ of Fe~XIX. Several sets of calculations including relativistic effects are carried…

Astrophysics · Physics 2009-10-31 Hong Lin Zhang , Anil K. Pradhan

Aimed at ionization balance and spectral analysis of UV and X-ray sources, we present self-consistent sets of photoionization cross sections, recombination cross sections, and rate coefficients for Li-like O VI and He-like O VII.…

Astrophysics · Physics 2009-11-07 Sultana N. Nahar , Anil K. Pradhan

Relativistic and resonance effects in the photoionization of Mg-like Fe~XV are investigated using the Breit-Pauli R-matrix Method (BPRM) at near-threshold and intermediate energies, complemented by the Relativistic Random Phase…

Astrophysics · Physics 2009-10-31 Nasreen Haque , Anil K. Pradhan

A comprehensive study of high-accuracy photoionization cross sections is carried out using the relativistic Breit-Pauli R-matrix (BPRM) method for (hnu + Fe XVII --> Fe XVIII + e). Owing to its importance in high-temperature plasmas the…

Solar and Stellar Astrophysics · Physics 2015-05-27 Sultana N. Nahar , Anil K. Pradhan , Guo-Xin Chen , Werner Eissner

We offer a theoretical and experimental study of the single-photon photoionization of Ne III. The high photon flux and the high-resolution capabilities of the Advanced Light Source at the LBNL were employed to measure absolute…

We present ground state photoionization cross sections of atoms and ions averaged over resonance structures for photoionization modeling of astrophysical sources. The detailed cross sections calculated in the close-coupling approximation…

Astrophysics · Physics 2009-10-30 M. A. Bautista , P. Romano , A. K. Pradhan

We are concerned with improving the diagnostic potential of the K lines and edges of elements with low cosmic abundances that are observed in the X-ray spectra of supernova remnants, galaxy clusters and accreting black holes and neutron…

Instrumentation and Methods for Astrophysics · Physics 2018-08-29 C. Mendoza , M. A. Bautista , P. Palmeri , P. Quinet , M. C. Witthoeft , T. R. Kallman

A theoretical investigation of photoabsorption and photoionization of Fe^{14+} extending beyond an earlier frame transformation R-matrix implementation is performed using a fully-correlated, Breit-Pauli R-matrix formulation including both…

Atomic Physics · Physics 2015-06-04 M. F. Hasoglu , T. W. Gorczyca , M. A. Bautista , Z. Felfli , S. T. Manson

We investigate the effect of resonances in photoionization and recombination cross sections computed using the R-matrix method. Photoionization and recombination rates derived from high-resolution cross sections for oxygen ions are compared…

Astrophysics · Physics 2009-11-10 Franck Delahaye , Sultana N. Nahar , Anil K Pradhan , Hong Lin Zhang

A general formulation is employed to study and quantitatively ascertain the effect of plasma broadening of {\it intrinsic} autoionizing (AI) resonances in photoionization cross sections. In particular, R-matrix data for iron ions described…

Solar and Stellar Astrophysics · Physics 2023-08-30 A. K. Pradhan

Relativistic and channel coupling effects in photoionization and unified electronic recombination of Fe XVII are demonstrated with an extensive 60-level close coupling calculation using the Breit-Pauli R-matrix method. Photoionization and…

Astrophysics · Physics 2009-11-06 Hong Lin Zhang , Sultana N. Nahar , Anil K. Pradhan

Extensive resonance structures are manifest in R-Matrix (RM) calculations. However, there exist a large number of highly excited electronic configurations that may contribute to background non-resonant bound-free opacity in high-temperature…

Solar and Stellar Astrophysics · Physics 2018-01-09 Lianshui Zhao , Werner Eissner , Sultana N. Nahar , Anil K. Pradhan

The first complete set of unified cross sections and rate coefficients are calculated for photoionization and recombination of He- and Li-like ions using the relativistic Breit-Pauli R-matrix method. We present total, unified (e + ion)…

Astrophysics · Physics 2016-08-30 Sultana N. Nahar , Anil K. Pradhan , Hong Lin Zhang

The photoionization of the four-electron beryllium-like isoelectronic series from the neutral to Fe^{+22} has been studied for ground ^1S and metastable ^3P initial states. The wave functions of the final-state (target) ions were built…

Atomic Physics · Physics 2012-05-28 W. -C. Chu , H. -L. Zhou , A. Hibbert , S. T. Manson

To investigate the completeness of coupled channel (CC) Breit-Pauli R-Matrix (BPRM) calculations for opacities, we employ the relativistic distorted wave (RDW) method to complement (``top-up'') and compare the BPRM photoionization cross…

Solar and Stellar Astrophysics · Physics 2023-08-30 L. Zhao , S. N. Nahar , W. Eissner , A. K. Pradhan

Relativistic close coupling calculations are reported for unified electronic recombination of (e + C IV) including non-resonant and resonant recombination processes, radiative and dielectronic recombination (RR and DR). Detailed comparison…

Astrophysics · Physics 2008-11-26 Anil K. Pradhan , Guo Xin Chen , Sultana N. Nahar , Hong Lin Zhang

A comprehensive study of relativistic and resonance effects in electron impact excitation of (e+Fe XVII) is carried out using the BPRM method in the relativistic close coupling approximation. Two sets of eigenfunction expansions are…

Astrophysics · Physics 2009-11-07 Guo-Xin Chen , Anil K. Pradhan , W. Eissner

Theoretically self-consistent calculations for photoionization and (e + ion) recombination are described. An identical eigenfunction expansion for the ion is employed in coupled channel calculations for both processes, thus ensuring…

Astrophysics · Physics 2007-05-23 Sultana N. Nahar

Photoionization and recombination cross sections and rate coefficients are calculated for Li-like Fe XXIV and He-like Fe XXV using the Breit-Pauli R-matrix (BPRM) method. A complete set of total and level-specific parameters is obtained to…

Astrophysics · Physics 2009-10-31 Sultana N. Nahar , Anil K. Pradhan , Hong Lin Zhang
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