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A unified scheme using the R-matrix method has been developed for electron-ion recombination subsuming heretofore separate treatments of radiative and dielectronic recombination (RR and DR). The ab initio coupled channel approach unifies…

Astrophysics · Physics 2009-11-10 Sultana N. Nahar , Anil K. Pradhan

We present R-matrix calculations of photoabsorption and photoionization cross sections across the K edge of the Li-like to Ca-like ions stages of Ni. Level-resolved, Breit-Pauli calculations were performed for the Li-like to Na-like stages.…

High Energy Astrophysical Phenomena · Physics 2015-05-28 M. C. Witthoeft , M. A. Bautista , J. Garcia , T. R. Kallman , C. Mendoza , P. Palmeri , P. Quinet

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

Using the photon-ion merged-beams technique at a synchrotron light source, we have measured relative cross sections for single and up to five-fold photoionization of Fe$^{2+}$ ions in the energy range 690--920 eV. This range contains…

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

Absolute cross sections for m-fold photoionization (m=1,...,6) of Fe+ by a single photon were measured employing the photon-ion merged-beams setup PIPE at the PETRA III synchrotron light source, operated by DESY in Hamburg, Germany. Photon…

Absolute photoionization cross sections for the Rb$^{2+}$ ion were recently measured at high resolution over the energy range 37.31 eV -- 44.08~eV, with autoionizing Rydberg resonance series identified, using the photon-ion merged-beam…

Atomic Physics · Physics 2019-06-05 Brendan M McLaughlin , James F Babb

Triple photoionization of Xe3+, Xe4+ and Xe5+ ions has been studied in the energy range 670-750 eV, including the 3d ionization threshold. The photon-ion merged-beam technique was used at a synchrotron light source to measure the absolute…

Results from large-scale theoretical cross section calculations for the total photoionization of the 4f, 5s, 5p and 6s orbitals of the neutral tungsten atom using the Dirac Coulomb R-matrix approximation (DARC: Dirac-Atomic R-matrix codes)…

Atomic Physics · Physics 2015-06-24 Connor P Ballance , Brendan M McLaughlin

High resolution measurements of photoionization cross sections for atomic ions are now being made on synchrotron radiation sources. The recent measurements by Kjeldsen etal. (1999) showed good agreement between the observed resonance…

Astrophysics · Physics 2009-11-06 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 solving the outstanding problem of solar opacity, and radiation transport plasma models in general, we report substantial photoabsorption in the high-energy regime due to atomic core photo-excitations not heretofore considered. In…

Solar and Stellar Astrophysics · Physics 2016-06-22 Sultana N. Nahar , Anil 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

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 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 present absolute L-shell photoionisation cross sections for the S+, S2+, S3+ions. The cross sections were obtained using the monochromatised photon beam delivered by the SOLEIL synchrotron source coupled with an ion beam extracted from…

Absolute photoionization cross-section calculations are presented for Se$^+$ using large-scale close-coupling calculations within the Breit-Pauli and Dirac-Coulomb R-matrix approximations. The results from our theoretical work are compared…

Earth and Planetary Astrophysics · Physics 2012-04-09 Brendan M. McLaughlin , Connor P. Ballance

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

Most astrophysical plasmas entail a balance between ionization and recombination. We present new results from the powerful R-matrix method which yields in an ab initio manner: (I) self-consistent photoionization and recombination cross…

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

Photoionization of neutral atomic sulfur in the ground and metastable states was studied experimentally at a photon energy resolution of 44 meV FWHM. Relative cross section measurements were recorded by using tunable vacuum ultraviolet…

Earth and Planetary Astrophysics · Physics 2015-06-23 Mathias Barthel , Roman Flesch , Eckart Rühl , Brendan M. McLaughlin
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