A programme is outlined for the assembly of a comprehensive dielectronic recombination database within generalized collisional--radiative (GCR) framework. It valid modelling ions elements in dynamic finite-density plasmas such as occur transient astrophysical solar flares and divertors high transport regions magnetic fusion devices. The resolution precision data are tuned to spectral analysis so sufficient prediction contributions individual line emissivities. fundamental structured...

Reliably interpreting spectra from electron-ionized cosmic plasmas requires accurate ionization balance calculations for the plasma in question. However, much of atomic data needed these have not been generated using modern theoretical methods and are often highly suspect. This translates directly into reliability collisional equilibrium (CIE) calculations. We make use state-of-the-art dielectronic recombination (DR) rate coefficients hydrogenic through Na-like ions all elements He up to...

The close-coupling approximation for electron-atom scattering is extended to include the effect of one-photon radiation damping at a level nonperturbative in wave function. complex potential derived and introduced directly into set integrodifferential equations used calculate S matrix. formulation ideal inelastic photoionization with can be photorecombination cross sections. numerical solution resulting differential equation accomplished through combination R-matrix, perturbation theory,...

We present high-resolution spectroscopy of the neon K-shell and iron L-shell interstellar absorption edges in nine X-ray binaries using High Energy Transmission Grating Spectrometer (HETGS) onboard Chandra Observatory. found that is well fit by an experimental determination cross-section for metallic iron, although with a slight wavelength shift ~20 mA. The edge region best model includes neutral three Gaussian lines. identify these lines as due to 1s-2p transitions from Ne II, III, IX. As...

Double photoionization accompanied by loss of $n$ C atoms ($n=0$, 2, 4, 6) was investigated merging beams Xe@C${}_{60}^{+}$ ions and synchrotron radiation measuring the yields product ions. The giant $4d$ dipole resonance caged Xe atom has a prominent signature in cross section for these channels, which together account 6.2 $\ifmmode\pm\else\textpm\fi{}$ 1.4 total oscillator strength 10. Compared to that free atom, is redistributed photon energy due multipath interference outgoing...

We have developed an alternative R-matrix with pseudostates (RMPS) method for incorporating a two-electron continuum description into the wavefunction of electron - ion collision calculations. This is similar in spirit to various recent treatments pseudostate expansion, most notably approaches Meyer and Greene, Bartschat et al. Our approach differs that we: (1) utilize direct sum several bases: physical target orbitals, additional MCHF pseudo-orbitals He ground state, and, on occasion,...

Extensive calculations of the atomic data required for spectral modelling K-shell photoabsorption oxygen ions have been carried out in a multi-code approach. The present level energies and wavelengths highly ionized species (electron occupancies 2 <= N 4) are accurate to within 0.5 eV 0.02 A, respectively. For > 4, lack measurements, wide experimental scatter, discrepancies among theoretical values handicaps reliable accuracy assessments. radiative Auger rates expected be 10% 20%,...

We present an X-ray absorption model for the interstellar medium, to be referred as ISMabs, that takes into account both neutral and ionized species of cosmically abundant elements, includes most accurate atomic data available. Using high-resolution spectra from eight binaries obtained with Chandra High Energy Transmission Grating Spectrometer, we proceed benchmark in particularly neon K-edge region. Compared previous photoabsorption models, which solely rely on species, inclusion ions leads...

Abstract We present absolute L-shell photoionisation cross sections for the S+, S2+, S3+ ions. The were obtained using monochromatised photon beam delivered by SOLEIL syn- chrotron source coupled with an ion extracted from electron cyclotron resonance (ECRIS) in merged dual-beam configuration. single, double and triple ionisation measured combined to generate total sections. For each of S2+ ions, energy regions corresponding excitation a 2p or 2s (∼ 175-230 eV) investigated. experimental...

Dielectronic recombination (DR) and radiative (RR) data for carbon-like ions forming nitrogen-like have been calculated as part of the assembly a level-resolved DR RR database necessary modelling dynamic finite-density plasmas (Badnell et al. [CITE]). Total rate coefficients are presented results discussed N+ to Zn24+, well Kr30+, Mo36+, Cd42+, Xe48+. We find that (no change in principal quantum number core electron) low-temperature does not scale smoothly with nuclear charge Z due...

Context. A comprehensive study of dielectronic recombination (DR) for the aluminum-like isoelectronic sequence has been completed.

An analytical formula is developed to represent accurately the photoabsorption cross section of O I for all energies interest in X-ray spectral modeling. In vicinity Kedge, a Rydberg series expression used fit R-matrix results, including important orbital relaxation effects, that predict absorption oscillator strengths below threshold and merge consistently continuously above-threshold section. Further minor adjustments are made order reliably align atomic resonances after consideration both...

We present absolute L-shell photoionisation cross sections for the S+, S2+, S3+ions. The were obtained using monochromatised photon beam delivered by SOLEIL synchrotron source coupled with an ion extracted from electron cyclotron resonance (ECRIS) in merged dual-beam configuration. single, double and triple ionisation measured combined to generate total sections. For each of S3+ ions, energy regions corresponding excitation a 2p or 2s (175-230 eV) investigated. experimental results are...

Dielectronic recombination (DR) and radiative (RR) data for oxygen-like ions forming fluorine-like have been calculated as part of the assembly a level-resolved DR RR database necessary modelling dynamic finite-density plasmas (Badnell et al. [CITE]). Total rate coefficients F+ to Zn22+ are presented results discussed. By comparison between perturbative R-matrix results, we find that RR/DR interference effects negligible even lowest-charged member. We also low-temperature (no change in...

Dielectronic recombination (DR) and radiative (RR) data for neon-like ions forming sodium-like systems has been calculated as part of the assembly a DR database necessary modelling dynamic and/or finite-density plasmas (Badnell et al. [CITE]). coefficients from Na+ to Zn20+, well Kr26+, Mo32+, Cd38+, Xe44+, are presented results discussed.

Partial and total dielectronic recombination (DR) rate coefficients for fluorine-like ions forming neon-like systems have been calculated as part of the assembly a final-state level-resolved DR database necessary modelling dynamic finite-density plasmas (Badnell et al. 2003). Calculations performed both ground metastable initial states Ne+ to Zn21+, well Kr27+, Mo33+, Xe45+. Results selection are presented discussed. We find that low-temperature DR, via core excitations involving no change...

It is demonstrated that the effect of a static cage potential on photoionization endohedrally enclosed atoms can be incorporated into standard $R$-matrix calculations using one two independent methods. For processes occurring entirely within fullerene, outer-region solutions modified by additional to yield phase-shifted Coulomb functions are matched inner-region $R$ matrix. Alternatively, if contained ``box,'' it directly formalism via simple one-electron integral contributions Hamiltonian,...

A recent experimental study [J.-E. Rubensson et al., Phys. Rev. Lett. 83, 947 (1999)] measured a significant fluorescence yield of the He( ${2lnl}^{\ensuremath{'}}$) photoexcited resonances, showing major qualitative differences from nonrelativistic predictions. We present further theoretical these states, and perform $R$-matrix multichannel quantum defect theory calculations to extract ionization cross sections. These results are in excellent agreement with newer, higher-resolution...

Using an R-matrix code recently developed by Robicheaux et al which includes a radiative optical potential, we have calculated electron-impact excitation cross sections to the n = 2 levels of and . We focus on resonance structure, find be significantly damped even for low-lying resonances, recent similar calculations Kisielius omit radiation damping overestimate contribution. For dielectronic recombination compare extent different approach Nahar Pradhan, uses inverse photoionization process...

Partial and total dielectronic recombination (DR) rate coefficients for fluorine-like ions forming neon-like systems have been calculated as part of the assembly a final-state level-resolved DR database necessary modelling dynamic finite-density plasmas (Badnell et al. 2003). Calculations performed both ground metastable initial states Ne to Zn21+, well Kr27+, Mo33+, Xe45+. Results selection are presented discussed. We find that low-temperature DR, via 2 → core excitations involving no...

We describe the atomic database of xstar spectral modeling code, summarizing systematic upgrades carried out in past twenty years to enable K-lines from chemical elements with number Z≤30 and recent extensions handle high-density plasmas. Such plasma environments are found, for instance, inner region accretion disks round compact objects (neutron stars black holes), which emit rich information about system’s physical properties. Our intention is offer a reliable tool take advantage...

Photoabsorption of neon in the region inner shell excited ${1s}^{\ensuremath{-}1}\mathrm{np}$ resonance series is treated using an optical potential R-matrix method. Compared to standard results, extremely broadened profile determined, due implicit inclusion core Auger decay states via potential, remarkably reproducing recent high-precision experimental results.

$K$-shell photodetachment from ${\mathrm{C}}^{\ensuremath{-}}$ has been investigated in the photon energy range between 280 and 285 eV using merged ion-beam--photon-beam technique. ions were produced a Cs sputtering negative-ion source, while photons by undulator beam line 10.0.1 of Advanced Light Source. ${\mathrm{C}}^{+}$ formed double detachment detected as function incident energy. Using this collinear arrangement, relative cross sections measured compared with theoretical predictions....

Time-dependent unrestricted Hartree-Fock (TDUHF) theory is formulated for the multiphoton ionization of a model atom. The single-particle states are nonorthogonal and quantum variational principle requires additional normalization terms. For He atom, three-dimensional (3D) electrostatic interaction replaced by 1D soft-core that allows construction two-electron atom in only two dimensions. resulting formulation TDUHF equations contains numerous exchange overlap rates found to be better...