Petascale computations for Large-scale Atomic and Molecular collisions

Petaflop architectures are currently being utilized efficiently to perform large scale computations in Atomic, Molecular and Optical Collisions. We solve the Schroedinger or Dirac equation for the appropriate collision problem using the R-matrix or R-matrix with pseudo-states approach. We briefly outline the parallel methodology used and implemented for the current suite of Breit-Pauli and DARC codes. Various examples are shown of our theoretical results compared with those obtained from Synchrotron Radiation facilities and from Satellite observations. We also indicate future directions and implementation of the R-matrix codes on emerging GPU architectures.Comment: 14 pages, 5 figures, 3 tables, Chapter in: Workshop on Sustained Simulated Performance 2013, Published by Springer, 2014, edited by Michael Resch, Yevgeniya Kovalenko, Eric Focht, Wolfgang Bez and Hiroaki Kobaysah

Sulphur X-ray absorption in the local ISM

We present a study S K-edge using high-resolution HETGS Chandra spectra of 36 low-mass X-ray binaries. For each source, we have estimated column densities for S I, S II, S III, S XIV, S XV, and S XVI ionic species, which trace the neutral, warm, and hot phases of the Galactic interstellar medium. We also estimated column densities for a sample of interstellar dust analogues. We measured their distribution as a function of Galactic latitude, longitude, and distances to the sources. While the cold-warm column densities tend to decrease with the Galactic latitude, we found no correlation with distances or Galactic longitude. This is the first detailed analysis of the sulphur K-edge absorption due to ISM using high-resolution X-ray spectra

K-shell photoionization of oxygen

Chinese Academy of Sciences;et al.;FEI;Institute of Physics Publishing Ltd;International Union of Pure and Applied Physics (IUPAP);National Natural Science Foundation of China28th International Conference on Photonic, Electronic and Atomic Collisions, ICPEAC 2013 -- 24 July 2013 through 30 July 2013 -- Lanzhou -- 106035R-matrix calculations of the 1s photoionization in oxygen are reported. Proper treatment of spectator Auger broadening, relaxation, pseudoresonace elimination, and shake-up/shake-off are addressed. © Published under licence by IOP Publishing Ltd

Photoionization of Xe@C60 using R-matrix methods

Chinese Academy of Sciences;et al.;FEI;Institute of Physics Publishing Ltd;International Union of Pure and Applied Physics (IUPAP);National Natural Science Foundation of China28th International Conference on Photonic, Electronic and Atomic Collisions, ICPEAC 2013 -- 24 July 2013 through 30 July 2013 -- Lanzhou -- 106035We report Breit-Pauli and Dirac R-matrix cross sections for the photoionization of endofullerene Xe@C60, showing strong confinement resonances, in excellent agreement with a recent experiment. © Published under licence by IOP Publishing Ltd

Nonmonotonic behavior as a function of nuclear charge of the K-shell Auger and radiative rates and fluorescence yields along the 1s2s(2)2p(3) isoelectronic sequence

Calculations using multiconfiguration Breit-Pauli and multiconfiguration Dirac-Fock methodologies have revealed that the radiative and Auger rates, and the associated fluorescence yields, of the six electron 1s2s(2)2p(3) K-shell vacancy isoelectronic sequence exhibit nonmonotonic behavior as a function of nuclear charge Z. This behavior is explained in terms of an accidental degeneracy, an avoided crossing of two nearly degenerate spin-orbit coupled levels. The results also demonstrate the importance of including both electron-electron correlation and spin-orbit effects even at low Z

Sulphur x-ray absorption in the local ısm

We present a study S K-edge using high-resolution HETGS Chandra spectra of 36 low-mass X-ray binaries. For each source, we have estimated column densities for S i, S ii, S iii, S xiv, S xv, and S xvi ionic species, which trace the neutral, warm, and hot phases of the Galactic interstellar medium. We also estimated column densities for a sample of interstellar dust analogues. We measured their distribution as a function of Galactic latitude, longitude, and distances to the sources. While the cold-warm column densities tend to decrease with the Galactic latitude, we found no correlation with distances or Galactic longitude. This is the first detailed analysis of the sulphur K-edge absorption due to ISM using high-resolution X-ray spectra. © 2023 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society

PAMOP: Petascale atomic, molecular and optical collision calculations

Petaflop architectures are currently being utilized efficiently to perform large scale computations in Atomic, Molecular and Optical Collisions. We solve the Schr\"odinger or Dirac equation for the appropriate collision problem using the R-matrix or R-matrix with pseudo-states approach. We briefly outline the parallel methodology used and implemented for the current suite of Breit-Pauli and DARC codes. In this report, various examples are shown from our theoretical results compared with experimental results obtained from Synchrotron Radiation facilities where the Cray architecture at HLRS is playing an integral part in our computational projects.Comment: 16 pages, 6 figures, Chapter 4, in High Performance Computing in Science and Engineering 2014, edited by W. E. Nagel, D. B. Kroner, and M. Reich (Springer, New York and Berlin, 2014). http://www.springer.com/mathematics/computational+science+%26+engineering/book/978-3-319-10809-

PAMOP Project: computations in support of experiments and astrophysical applications

Our computation effort is primarily concentrated on support of current and future measurements being carried out at various synchrotron radiation facilities around the globe, and photodissociation computations for astrophysical applications. In our work we solve the Schr\"odinger or Dirac equation for the appropriate collision problem using the R-matrix or R-matrix with pseudo-states approach from first principles. The time dependent close-coupling (TDCC) method is also used in our work. A brief summary of the methodology and ongoing developments implemented in the R-matrix suite of Breit-Pauli and Dirac-Atomic R-matrix codes (DARC) is presented.Comment: 17 pages, 10 figures: chapter in the book, High Performance Computing in Science and Engineering'16, edited by W. E. Nagel, D. B. Kr\"oner, and M. Reich (Springer, New York and Berlin, 2017