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Abstract.A programme is outlined for the assembly of a comprehensive dielectronic recombination database within the generalized collisional-radiative (GCR) framework. It is valid for modelling ions of elements in dynamic finite-density plasmas such as occur in transient astrophysical plasmas such as solar flares and in the divertors and high transport regions of magnetic fusion devices. The resolution and precision of the data are tuned to spectral analysis and so are sufficient for prediction of the dielectronic recombination contributions to individual spectral line emissivities. The fundamental data are structured according to the format prescriptions of the Atomic Data and Analysis Structure (ADAS) and the production of relevant GCR derived data for application is described and implemented following ADAS. The requirements on the dielectronic recombination database are reviewed and the new data are placed in context and evaluated with respect to older and more approximate treatments. Illustrative results validate the new high-resolution zero-density dielectronic recombination data in comparison with measurements made in heavy-ion storage rings utilizing an electron cooler. We also exemplify the role of the dielectronic data on GCR coefficient behaviour for some representative light and medium weight elements.

LXCat is an open‐access platform (http://www.lxcat.net) for curating data needed for modeling the electron and ion components of technological plasmas. The data types presently supported on LXCat are scattering cross sections and swarm/transport parameters, ion‐neutral interaction potentials, and optical oscillator strengths. Twenty‐four databases contributed by different groups around the world can be accessed on LXCat. New contributors are welcome; the database contributors retain ownership and are responsible for the contents and maintenance of the individual databases. This article summarizes the present status of the project.

The O i 777 nm triplet is a key diagnostic of oxygen abundances in the atmospheres of FGK-type stars; however, it is sensitive to departures from local thermodynamic equilibrium (LTE). The accuracy of non-LTE line formation calculations has hitherto been limited by errors in the inelastic O+H collisional rate coefficients; several recent studies have used the Drawin recipe, albeit with a correction factor S H that is calibrated to the solar centre-to-limb variation of the triplet. We present a new model oxygen atom that incorporates inelastic O+H collisional rate coefficients using an asymptotic two-electron model based on linear combinations of atomic orbitals, combined with a free electron model based on the impulse approximation. Using a 3D hydrodynamic stagger model solar atmosphere and 3D non-LTE line formation calculations, we demonstrate that this physically motivated approach is able to reproduce the solar centre-to-limb variation of the triplet to 0.02 dex, without any calibration of the inelastic collisional rate coefficients or other free parameters. We infer log O = 8.69±0.03 from the triplet alone, strengthening the case for a low solar oxygen abundance.

The basic ideas of the B-spline R-matrix (BSR) approach are reviewed, and the use of the method is illustrated with a variety of applications to atomic structure, electron–atom collisions and photo-induced processes. Special emphasis is placed on complex, open-shell targets, for which the method has proven very successful in reproducing, for example, a wealth of near-threshold resonance structures. Recent extensions to a fully relativistic framework and intermediate energies have allowed for an accurate treatment of heavy targets as well as a fully nonperturbative scheme for electron-impact ionization. Finally, field-free BSR Hamiltonian and electric dipole matrices can be employed in the time-dependent treatment of intense short-pulse laser–atom interactions.

We revisit the time-resolved photoemission in neon atoms as probed by attosecond streaking. We calculate streaking time shifts for the emission of 2p and 2s electrons and compare the relative delay as measured in a recent experiment by Schultze et al. [Science 328, 1658[Science 328, (2010]. The B-spline R-matrix method is employed to calculate accurate Eisenbud-Wigner-Smith time delays from multielectron dipole transition matrix elements for photoionization. The additional laser field-induced time shifts in the exit channel are obtained from separate, time-dependent simulations of a full streaking process by solving the time-dependent Schrödinger equation on the single-active-electron level. The resulting accurate total relative streaking time shifts between 2s and 2p emission lie well below the experimental data. We identify the presence of unresolved shake-up satellites in the experiment as a potential source of error in the determination of streaking time shifts.

Large-scale R-matrix-with-pseudostates calculations for electron collisions with argon atoms, using a recently developed parallel version of our B-spline R-matrix code, are reported. The calculations were carried out in the semirelativistic jK-coupling scheme. They are intended to provide converged (with respect to the number of coupled states) results for electron-impact excitation of individual target states with dominant configurations 3p 5 4s, 3p 5 4p, 3p 5 3d, and 3p 5 5s for incident electron energies from threshold to 300 eV. The close-coupling expansion includes 500 target states, with the lowest 78 states representing the bound spectrum and the remaining 422 the ionization continuum. The results reveal dramatic reductions of the predicted excitation cross sections at intermediate energies due to a strong influence of coupling to the target continuum and the higher-lying Rydberg states. Comparison with available experimental data for excitation raises questions about the absolute normalization in the measurements.

7An analytical formula is developed to represent accurately the photoabsorption cross section of O I for all energies of interest in X-ray spectral modeling.In the vicinity of the K edge, a Rydberg series expression is used to fit R-matrix results, including important orbital relaxation effects, that accurately predict the absorption oscillator strengths below threshold and merge consistently and continuously to the above-threshold cross section. Further minor adjustments are made to the threshold energies in order to reliably align the atomic Rydberg resonances after consideration of both experimental and observed line positions. At energies far below or above the K-edge region, the formulation is based on both outer-and inner-shell direct photoionization, including significant shakeup and shake-off processes that result in photoionization-excitation and double photoionization contributions to the total cross section. The ultimate purpose for developing a definitive model for oxygen absorption is to resolve standing discrepancies between the astronomically observed and laboratory measured line positions, and between the inferred atomic and molecular oxygen abundances in the interstellar medium from xstar and spex spectral models.Subject headings: X-rays: ISM -ISM: atoms -atomic processes -line: formation -8 line: profiles 9 Atomic photoionization, an important astrophysical process, has been studied for 11 more than a century since the seminal understanding of its energetics by Einstein (1905) 12 and the first calculations of quantum mechanical cross sections (Bates 1939). Over the 13 years, a plethora of experimental and theoretical investigations have managed an excellent 14 grasp of its physics (Fano & Cooper 1968; Starace 1982), together with a remarkable 15 quantitative description of the valence-shell photoionization of atoms and atomic ions 16 (Opacity Project Team 1995, 1997). However, the quantitative model of inner-shell 17 photoabsorption is less sound due to a variety of relaxation processes, namely Auger and 18 X-ray emission, that must be taken into account in order to achieve acceptable accuracy, 19 especially in the near-threshold region. 20 Inner-shell photoabsorption of metals with nuclear charge 7 ≤ Z ≤ 28 is directly 21 accessible to modern X-ray observatories such as Chandra and XMM-Newton, and, hence, 22 is of much interest in astronomy. Particularly prominent in the photoabsorption of the 23 interstellar medium (ISM) are the K-shell features (lines and edges) of atomic oxygen, 24 which is the most abundant metal and is critically important in the energetic and chemical 25 evolution of the Universe (Stasińska et al. 2012). At present, though, the unsatisfactory 26 quantitative understanding of oxygen inner-shell photoabsorption is such that there exists 27 various sets of cross sections, each one leading to different conclusions regarding the 28 ionization and atomic-to-molecular fractions in the ISM along various Galactic lines of 29 sight. 30 The first inner-shell photoabsorption cross se...