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Future X-ray astrophysics experiments require multiplexed readout of high fill-factor, kilo-pixel arrays of transition-edge sensors (TESs), with very high spectral resolution over a broad range of energies. In this paper we report on a prototype kilo-pixel array of Mo/Au TESs readout with 8-column by 32-row time-division multiplexing (TDM). This system is being used to demonstrate the critical detector and readout technology for ESA's Athena X-IFU, and when complete will be used in laboratory astrophysics experiments. Our array and TDM readout have demonstrated a combined full-width-at-half-maximum energy resolution, including > 200 pixels, of: 1.95 eV for Ti-Kα (4.5 keV), 1.97 eV for Mn-Kα (5.9 keV), 2.16 eV for Co-Kα (6.9 keV), 2.33 eV for Cu-Kα (8 keV), 3.26 eV for Br-Kα (11.9 keV). The 1 sigma statistical errors are ≤0.01 eV for all spectra. These results meet the broad-band resolution requirements for X-IFU with margin.

We report on the development of multi-absorber transition edge sensors (TESs), referred to as hydras. A hydra consists of multiple x-ray absorbers each with a different thermal conductance to a TES. Position information is encoded in the pulse shape. With some trade-off in performance, hydras enable very large format arrays without the prohibitive increase in bias and read-out components associated with arrays of individual TESs. Hydras are under development for the next generation of space telescope such as Lynx. Lynx is a NASA concept under study that will combine a < 1 arcsecond angular resolution optic with 100,000-pixel microcalorimeter array with energy resolution of deltaE_FWHM ~ 3 eV in the soft x-ray energy range. We present first results from hydras with 25-pixels for Lynx. Designs with absorbers on a 25 micron and 50 micron pitch are studied. Arrays incorporate, for the first time, microstrip buried wiring layers of suitable pitch and density required to readout a full-scale Lynx array. The resolution from the coadded energy histogram including all 25-pixels was deltaE_FWHM = 1.66+/-0.02 eV and 3.34+/-0.06 eV at an energy of 1.5 keV for the 25 micron and 50 micron absorber designs respectively. Position discrimination is demonstrated from parameterization of the rise-time., 7 pages, 5 figures. Low Temperature Detectors 18 Conference, Milan Italy

We describe the atomic database of the XSTAR spectral modeling code, summarizing the systematic upgrades carried out in the past twenty years to enable the modeling of K lines from chemical elements with atomic number $Z\leq 30$ and recent extensions to handle high-density plasmas. Such plasma environments are found, for instance, in the inner region of accretion disks round compact objects (neutron stars and black holes), which emit rich information about the system physical properties. Our intention is to offer a reliable modeling tool to take advantage of the outstanding spectral capabilities of the new generation of X-ray space telescopes (e.g., XRISM and ATHENA) to be launched in the coming years. Data curatorial aspects are discussed and an updated list of reference sources is compiled to improve the database provenance metadata. Two XSTAR spin-offs -- the ISMabs absorption model and the uaDB database -- are also described., Comment: 36 pages, 11 figures

We present a test platform for the Athena X-IFU detection chain, which will serve as the first demonstration of the representative end-to-end detection and readout chain for the X-IFU, using prototypes of the future flight electronics and currently available subsystems. This test bench, housed in a commercial two-stage ADR cryostat, includes a focal plane array placed at the 50 mK cold stage of the ADR with a kilopixel array of transition-edge sensor microcalorimeter spectrometers and associated cold readout electronics. Prototype room temperature electronics for the X-IFU provide the readout, and will evolve over time to become more representative of the X-IFU mission baseline. The test bench yields critical feedback on subsystem designs and interfaces, in particular the warm readout electronics, and will provide an in-house detection system for continued testing and development of the warm readout electronics and for the validation of X-ray calibration sources. In this paper, we describe the test bench subsystems and design, characterization of the cryostat, and current status of the project., Comment: 11 pages, 4 figures, to appear in Proc. SPIE Astronomical Telescopes and Instrumentation, 2020

The X-Ray Imaging and Spectroscopy Mission (XRISM) is the successor to the 2016 Hitomi mission that ended prematurely. Like Hitomi, the primary science goals are to examine astrophysical problems with precise highresolution X-ray spectroscopy. XRISM promises to discover new horizons in X-ray astronomy. XRISM carries a 6 x 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly and a co-aligned X-ray CCD camera that covers the same energy band over a large field of view. XRISM utilizes Hitomi heritage, but all designs were reviewed. The attitude and orbit control system were improved in hardware and software. The number of star sensors were increased from two to three to improve coverage and robustness in onboard attitude determination and to obtain a wider field of view sun sensor. The fault detection, isolation, and reconfiguration (FDIR) system was carefully examined and reconfigured. Together with a planned increase of ground support stations, the survivability of the spacecraft is significantly improved.

This is the final report of a three-paper series on the K-shell photoabsorption and photoionization of trace elements, namely F, Na, P, Cl, K, Sc, Ti, V, Cr, Mn, Co, Cu and Zn. K lines and edges from such elements are observed in the X-ray spectra of supernova remnants, galaxy clusters and accreting black holes and neutron stars, their diagnostic potential being limited by poor atomic data. We are completing the previously reported radiative datasets with new photoabsorption and photoionization cross sections for isoelectronic sequences with electron number $19\leq N\leq 26$. We are also giving attention to the access, integrity and usability of the whole resulting atomic database. Target representations are obtained with the atomic structure code AUTOSTRUCTURE. Where possible, cross sections for ground-configuration states are computed with the Breit--Pauli $R$-matrix method (BPRM) in either intermediate or $LS$ coupling including damping (radiative and Auger) effects; otherwise and more generally, they are generated in the isolated-resonance approximation with AUTOSTRUCTURE. Cross sections were computed with BPRM only for the K ($N=19$) and Ca ($N=20$) isoelectronic sequences, the latter in $LS$ coupling. For the rest of the sequences ($21\leq N \leq 26$), AUTOSTRUCTURE was run in $LS$-coupling mode taking into account damping effects. Comparisons between these two methods for K-like Zn XII and Ca-like Zn XI show that, to ensure reasonable accuracy, the $LS$ calculations must be performed taking into account the non-fine-structure relativistic corrections., 7 pages, 3 figures. Accepted for publication in Astronomy & Astrophysics

We describe the tools and the underlying methods and principles for generating the spectral response functions for the four imaging instruments that were flown on the Hitomi x-ray astronomy satellite [Soft X-ray Spectrometer, or SXS; Soft X-ray Imager, or SXI, and two Hard X-ray Imagers, or HXI]. In essence, the spectral response function is a temporally and spatially averaged effective area and line-spread-function. For model-fitting x-ray spectra from an instrument, the spectral response function encapsulates the end-to-end physics of the entire system from telescope to detector, and also includes satellite attitude drift, exposure corrections, and in the case of the HXIs, drift in the telescope/detector alignment system. Accuracy in the construction of the spectral response functions is, therefore, critical to maximize the science return from the data.

We present an introduction to the heasim multimission observation and skyback background, high-energy pseudo Monte Carlo astrophysical simulation tools. Heasim may be used to accurately and efficiently construct flexible image transport system (FITS) event files for simple or composite sources with a wide range of standard and user-defined spatial, spectral, and temporal characteristics. Skyback is designed to enable users to assess the impact of background discrete and diffuse emission on prospective observations, and skyback output may be directly input into heasim. We present a brief overview of heasim and skyback input, algorithms, usage, and output. We also introduce the sxsbranch tool that computes Hitomi soft X-ray spectrometer resolution grade branching ratios, emphasizing its application to simulations. We include several examples of particular relevance to the Hitomi mission.

There have been long outstanding requests from the modeling community for uncertainty estimates on atomic data. This paper outlines a systematic approach from fundamental atomic structure and collisional calculations, through to well-known spectral diagnostic lines, correlating the uncertainties from each contributing process.

Astro-H (Hitomi) is an X-ray/Gamma-ray mission led by Japan with international participation, launched on February 17, 2016. The payload consists of four different instruments (SXS, SXI, HXI and SGD) that operate simultaneously to cover the energy range from 0.3 keV up to 600 keV. This paper presents the analysis software and the data processing pipeline created to calibrate and analyze the Hitomi science data along with the plan for the archive and user support. These activities have been a collaborative effort shared between scientists and software engineers working in several institutes in Japan and USA.

Over the last several years, our group has undertaken a systematic investigation of atomic properties of K-vacancy states in many ions. More precisely, reliable data such as level energies, wavelengths, Einstein A-coefficients, radiative and Auger widths were computed for a large number of ions using three different atomic structure theoretical approaches, i.e. relativistic Hartree–Fock (HFR), AUTOSTRUCTURE (AS) and multiconfiguration Dirac–Fock (MCDF) methods. Extensive calculations of photoabsorption and photoionization cross sections were also performed using the Breit–Pauli R-matrix method including the effects of radiative and Auger damping by means of an optical potential. Here, we report on our overall progress concerning N, O, Ne, Mg, Al, Si, S, Ar, Ca, Fe and Ni ions.

Successfully modeling X-ray emission from astrophysical plasmas requires a wide range of atomic data to be rapidly accessible by modeling codes, enabling calculation of synthetic spectra for fitting with observations. Over many years the astrophysical databases have roughly kept pace with the advances in detector and spectrometer technology. We outline here the basic atomic processes contributing to the emission from different types of plasmas and briefly touch on the difference between the methods used to calculate this data. We then discuss in more detail the different issues addressed by atomic databases in regards to what data to store and how to make it accessible. Finally, the question of the effect of uncertainties in atomic data is explored, as a reminder to observers that atomic data is not known to infinite precision, and should not be treated as such.

We present extensive computations of photoabsorption and photoionization cross sections across the K-edge of Ne, Mg, Si, S, Ar, and Ca ions with less than 11 electrons. The calculations are performed using the Breit-Pauli R-matrix method and include the effects of radiative and Auger damping by means of an optical potential. The wave functions are constructed from single-electron orbital bases obtained using a Thomas-Fermi-Dirac statistical model potential. Configuration interaction is considered among all fine-structure levels within the n = 2 complex. The damping processes affect the resonances converging to the K thresholds causing them to display symmetric profiles of constant width that smear the otherwise sharp edge at the photoionization thresholds.

Spectroscopy of planetary nebulae (PNe) provides the means to investigate s-process enrichments of neutron(n)-capture elements that cannot be detected in asymptotic giant branch (AGB) stars. However, accurate abundance determinations of these elements present a challenge. Corrections for unobserved ions can be large and uncertain, since in many PNe only one ion of a given n-capture element has been detected. Furthermore, the atomic data governing the ionization balance of these species are not well-determined, inhibiting the derivation of accurate ionization corrections. We present initial results of a program that addresses these challenges. Deep high resolution optical spectroscopy of ~20 PNe has been performed to detect emission lines from trans-iron species including Se, Br, Kr, Rb, and Xe. The optical spectral region provides access to multiple ions of these elements, which reduces the magnitude and importance of uncertainties in the ionization corrections. In addition, experimental and theoretical efforts are providing determinations of the photoionization cross-sections and recombination rate coefficients of Se, Kr, and Xe ions. These new atomic data will make it possible to derive robust ionization corrections for these elements. Together, our observational and atomic data results will enable n-capture element abundances to be determined with unprecedented accuracy in ionized nebulae., Comment: 6 pages, 6 figures, to appear in "The Origin of the Elements Heavier than Fe", Sep 25-27, 2008, Turin, Italy, PASA, eds. John C. Lattanzio and M. Lugaro

We present R-matrix results for the electron-impact excitation of Fe6+. The intermediate-coupling frame transformation (ICFT) method has been used to obtain level-resolved collision strengths. We then calculate effective collision strengths assuming a Maxwellian distribution for the incident electron velocities. A large configuration interaction (CI) expansion of 1896 LS terms (4776 fine-structure levels) is used to obtain an accurate target. This is reduced to 89 close-coupling (CC) terms (189 levels) for the scattering calculation. To investigate the importance of CI, we also perform a second calculation with the same CC expansion but a smaller CI expansion. We discuss the difficulties of such a comparison and look at which transitions show the most sensitivity to the CI expansion. Our effective collision strengths are compared with a previous IRON Project report (Berrington et al. 2000, A&A, 142, 313) for transitions within the ground configuration and a recent distorted wave calculation (Zeng et al. 2005, MNRAS, 357, 440) for transitions to excited configurations. We find good agreement with the results of the previous R-matrix calculation and with the high-temperature distorted-wave results for most transitions, although there are some significant differences at lower temperatures in the latter case.

We present results for the electron-impact excitation of F-like ions from Ne+ to Kr27+ using an R-matrix approach where the intermediate-coupling frame transformation method has been used to obtain level-resolved collision strengths. For each calculation, the target has been expanded using 87 terms (195 levels) with the following configuration basis: 2s2 2p5, 2s 2p6, 2s2 2p4 3l, 2s 2p5 3l and 2s2 2p4 4l. Comparisons are made with previous R-matrix calculations for the fine-structure transition over the whole sequence and other, more extensive, calculations on Ne+ and Fe17+. We examine iso-electronic trends of both low- and high-temperature effective collision strengths. This complete, self-consistent set of radiative and collision data is archived in multiple databases.

We review de development of the time-dependent close-coupling method to study atomic and molecular few body dynamics. Applications include electron and photon collisions with atoms, molecules, and their ions. Fil: Pindzola, M. S.. Auburn University; Estados Unidos Fil: Robicheaux, F.. Auburn University; Estados Unidos Fil: Loch, S. D.. Auburn University; Estados Unidos Fil: Berengut, J. C.. Auburn University; Estados Unidos Fil: Topcu, T.. Auburn University; Estados Unidos Fil: Colgan, J.. Los Alamos National Laboratory; Estados Unidos Fil: Foster, M.. Los Alamos National Laboratory; Estados Unidos Fil: Griffin, D. C.. Rollins College,; Estados Unidos Fil: Ballance, C. P.. Rollins College,; Estados Unidos Fil: Schultz, D. R.. Oak Ridge National Laboratory; Estados Unidos Fil: Minami, T.. Oak Ridge National Laboratory; Estados Unidos Fil: Badnell, N. R.. University Of Strathclyde; Reino Unido Fil: Witthoeft, M. C.. University Of Strathclyde; Reino Unido Fil: Plante, D. R.. Stetson University; Estados Unidos Fil: Mitnik, Dario Marcelo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina Fil: Ludlow, J. A.. Queen’s University; Reino Unido Fil: Kleiman, U.. Max Planck Institute for the Physics of Complex Systems; Alemania

We present results for the electron-impact excitation of N-like Fe as part of the RmaX network. R-matrix theory using an intermediatecoupling frame transformation method is used to obtain level-resolved collision strengths. Separate calculations are performed using different target expansions. The first is a 215 level close-coupling calculation which has the 2s 2 2p 3 ,2 s 2p 4 ,2 p 5 ,2 s 2 2p 2 3l, and 2s 2p 3 3l configurations while the second calculation also includes the levels from the 2s 2 2p 2 4l configurations for a total of 302 close-coupling levels. The effect of the additional resonant enhancement of the larger calculation is explored and compared with a previous IRON Project report and other, more recent, calculations. As a final comparison, we model an astrophysical plasma using the results of the present calculations and previous work.

A first stage collision database is assembled which contains electron-impact effective collision strengths, and ionization and recombination rate coefficients for Li, Li+, and Li2+. The first stage database is constructed using the R-matrix with pseudo-states, time-dependent close-coupling, converged close-coupling, and perturbative distorted-wave methods. A second stage collision database is then assembled which contains generalized collisional-radiative and radiated power loss coefficients. The second stage database is constructed by solution of collisional-radiative equations in the quasi-static equilibrium approximation using the first stage database. Both collision database stages reside in electronic form at the ORNL Controlled Fusion Atomic Data Center and in the ADAS database, and are easily accessed over the worldwide internet. Fil: Loch, S. D.. Auburn University; Estados Unidos Fil: Colgan, J.. Auburn University; Estados Unidos Fil: Witthoeft, M. C.. Auburn University; Estados Unidos Fil: Pindzola, M. S.. Auburn University; Estados Unidos Fil: Ballance, C. P.. Rollins College; Estados Unidos Fil: Mitnik, Dario Marcelo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina. Rollins College; Estados Unidos Fil: Griffin, D. C.. Rollins College; Estados Unidos Fil: O'Mullane, M. G.. University of Strathclyde; Reino Unido Fil: Badnell, N. R.. University of Strathclyde; Reino Unido Fil: Summers, H. P.. University of Strathclyde; Reino Unido

The flow of a Bose–Einstein condensate through smooth and corrugated waveguides is studied by direct numerical solution of the time-dependent Gross–Pitaevskii equation. One end of each waveguide has a teacup longitudinal potential, which when lowered generates a quasi-continuous supersonic flow. As the nonlinear strength factor, which is proportional to the scattering length times the number of atoms, becomes more positive, we find that the condensate broadens and moves more rapidly down a smooth waveguide. For a given nonlinear strength factor, an increase in the size of corrugations in the waveguide, used to simulate imperfections in experimental structures, has a noticeable effect on condensate flow. However, for a given corrugation size, an increase in the condensate flow is always observed when the nonlinear strength factor is increased.

We present results for electron-impact excitation of F-like Fe calculated using R-matrix theory where an intermediate-coupling frame transformation (ICFT) is used to obtain level-resolved collision strengths. Two such calculations are performed, the first expands the target using 2s 2 2p 5 ,2 s 2p 6 ,2 s 2 2p 4 3l ,2 s 2p 5 3l, and 2p 6 3l configurations while the second calculation includes the 2s 2 2p 4 4l ,2 s 2p 5 4l, and 2p 6 4l configurations as well. The effect of the additional structure in the latter calculation on the n = 3 resonances is explored and compared with previous calculations. We find strong resonant enhancement of the effective collision strengths to the 2s 2 2p 4 3s levels. A comparison with a Chandra X-ray observation of Capella shows that the n = 4 R-matrix calculation leads to good agreement with observation.

To test the validity of classical trajectory and perturbative quantal methods for electron-impact ionization of H-like ions from excited states, we have performed advanced close-coupling calculations of ionization from excited states in H, Li2+ and B4+ using the R-matrix with pseudo states and the time-dependent close-coupling methods. Comparisons with our classical trajectory Monte Carlo (CTMC) and distorted-wave (DW) calculations show that the CTMC method is more accurate than the DW method for H, but does not improve with n and grows substantially worse with Z, while the DW method improves with Z and grows worse with n.

The ASTRO-H, which will be launched in 2015, is the sixth in a series of Japanese X-ray satellites. It is an international mission led by JAXA in collaboration with NASA and ESA, aiming to observe astrophysical objects in the X-ray band from 0.5 to 600 keV. One of the important scientific goals is to understand physical processes in the extreme environments of active and variable astrophysical objects, such as black holes, neutron stars, binary star, and active galactic nuclei. Therefore, a fast timing capability is a key requirement for the mission. According to numerical estimates of scientific performance, absolute times of X-ray events are required to have an accuracy of 300 µs to achieve minimum scientific goals and an accuracy of 30 µs is desired as a goal. The satellite carries a GPS receiver to get the accurate time information, which is distributed from the central computer on board through the large-and-complex SpaceWire network. Distributions of time information are shared in the same lines used for communications of telemetry and commands, and thus propagation delays and jitters affect the timing accuracy of the payload instruments. Further six items are identified as sources of timing errors and are measured on ground to be used in the calibration by off-line software. The time-assignment tasks in the off-line software packages are designed to be common for all the scientific instruments, although the hardware designs for finer timing resolutions are different by the instruments. Measurements of propagation delays in the flight configuration on ground and in-orbit calibration plans are described. The detail description will be submitted to the IEEE TNS paper in near future. This work demonstrates a good example of care points for space-use instruments in the hardware-and-software designs and calibration measurements in order to achieve a fine timing resolution at the micro second order with the middle-sized satellites using the SpaceWire (IEEE1355) network.

Excitation of a model hydrogen atom by a coherent electron beam is calculated by direct solution of the time-dependent Schrodinger equation on a three-dimensional lattice. The Coulomb interaction between the electrons is described by v(r1,r2) = 1/r> and all angular momenta are set to zero. The coherent beam consists of moving wavepackets for each of two free electrons which arrive at the third bound electron at different times. As recently predicted by Robicheaux and Noordam (2000 Phys. Rev. Lett. 84 3735), the probability for a weak excitation should vary as a function of arrival time. The time-dependent calculations for the model hydrogen atom show that the 1s → 2s excitation probability oscillates about an axis which is between one and two times the excitation probability from only one wavepacket. The frequency of the probability oscillation is found to be equal to the 1s → 2s transition frequency. Large destructive interference of the 1s → 2s cross section is illustrated by contour maps of the 2s projected probability as a function of wavepacket arrival time.

We present multi-configuration Breit-Pauli AUTOSTRUCTURE calculations of distorted-wave photoionization (PI) cross sections, and total and partial final-state resolved radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for the first six ions of the trans-iron element Se. These calculations were motivated by the recent detection of Se emission lines in a large number of planetary nebulae. Se is a potentially useful tracer of neutron-capture nucleosynthesis, but accurate determinations of its abundance in photoionized nebulae have been hindered by the lack of atomic data governing its ionization balance. Our calculations were carried out in intermediate coupling with semi-relativistic radial wavefunctions. PI and recombination data were determined for levels within the ground configuration of each ion, and experimental PI cross-section measurements were used to benchmark our results. For DR, we allowed dn=0 core excitations, which are important at photoionized plasma temperatures. DR is the dominant recombination process for each of these Se ions at temperatures representative of photoionized nebulae (~10^4 K). To estimate the uncertainties of these data, we compared results from three different configuration-interaction expansions for each ion, and tested the sensitivity of the results to the radial scaling factors in the structure calculations. We find that the internal uncertainties are typically 30-50% for the direct PI cross sections and ~10% for the computed RR rate coefficients, while those for low-temperature DR can be considerably larger (from 15-30% up to two orders of magnitude) due to the unknown energies of near-threshold autoionization resonances. The results are suitable for incorporation into photoionization codes used to numerically simulate astrophysical nebulae, and will enable robust determinations of nebular Se abundances., 17 pages, 8 figures, accepted for publication in Astronomy and Astrophysics

Neutron(n)-capture elements (atomic number Z>30), which can be produced in planetary nebula (PN) progenitor stars via s-process nucleosynthesis, have been detected in nearly 100 PNe. This demonstrates that nebular spectroscopy is a potentially powerful tool for studying the production and chemical evolution of trans-iron elements. However, significant challenges must be addressed before this goal can be achieved. One of the most substantial hurdles is the lack of atomic data for n-capture elements, particularly that needed to solve for their ionization equilibrium (and hence to convert ionic abundances to elemental abundances). To address this need, we have computed photoionization cross sections and radiative and dielectronic recombination rate coefficients for the first six ions of Se and Kr. The calculations were benchmarked against experimental photoionization cross section measurements. In addition, we computed charge transfer (CT) rate coefficients for ions of six n-capture elements. These efforts will enable the accurate determination of nebular Se and Kr abundances, allowing robust investigations of s-process enrichments in PNe., To be published in IAU Symp. 283: Planetary Nebulae, an Eye to the Future; 2 pages

As computer power continues to increase, so does our ability to carry out extensive, non‐perturbative calculations of atomic processes. Much work has been done on increasing the target representation of complex systems in step with advances in computational power. However there is also a need for coverage in terms of atomic data used in astrophysical or fusion plasma modeling. In this talk, we discuss recent R‐matrix calculations of electron‐impact excitation and photoionization over iso‐electronic sequences. While automation of R‐matrix codes and data analysis are reviewed, the talk is focused on iso‐electronic trends observed in the data. Specifically, we show the effect that resonant enhancement and level mixing can have on expected iso‐electronic trends.

Radiative and Auger decay data have been calculated for modelling the K lines in ions of the nickel isonuclear sequence, from Ni$^+$ up to Ni$^{27+}$. Level energies, transition wavelengths, radiative transition probabilities, and radiative and Auger widths have been determined using Cowan's Hartree--Fock with Relativistic corrections (HFR) method. Auger widths for the third-row ions (Ni$^+$--Ni$^{10+}$) have been computed using single-configuration average (SCA) compact formulae. Results are compared with data sets computed with the AUTOSTRUCTURE and MCDF atomic structure codes and with available experimental and theoretical values, mainly in highly ionized ions and in the solid state., Comment: submitted to ApJS. 42 pages. 12 figures

A joint theoretical and experimental investigation is made of the influence of long-lived metastable levels on the electron-impact single ionization of ${\mathrm{C}}^{2+}$. It is expected that our electron cyclotron resonance ion source produces a beam with 40% of the ${\mathrm{C}}^{2+}$ ions in the $1{s}^{2}2{s}^{2}\phantom{\rule{0.3em}{0ex}}^{1}S_{0}$ ground level and 60% in the $1{s}^{2}2s2p\phantom{\rule{0.3em}{0ex}}^{3}P_{0,2}$ excited levels. The comparison of nonperturbative close-coupling calculations with previous single-pass crossed beams and with our multiple-pass storage-ring measurements for the electron-impact ionization of ${\mathrm{C}}^{2+}$ is consistent with the predicted large metastable fraction. Reasonable agreement is found between the present time-dependent close-coupling, $R$-matrix with pseudostates, and converged-close-coupling ionization cross-section calculations for the ground and first excited configuration, and experimental measurement, assuming a 60% metastable fraction in the ion beam. Distorted-wave calculations are found to overestimate the ionization cross section from both the ground and metastable terms, compared with nonperturbative calculations, resulting in an overestimation of the resultant total cross section when compared with experiment. It is clear that collisional-radiative modeling of the evolution of atomic plasmas through the Be-like ionization stage will need to take into account the role of both ground and metastable levels.

We present experimental measurements and theoretical calculations for the electron-impact single ionization cross section of ${\mathrm{Sc}}^{+}$ ions covering an energy range from threshold to $1000\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. An electron-ion crossed-beams setup was employed for the measurements of absolute cross sections as well as for a high-resolution energy scan to uncover fine details in the energy dependence of the cross section. Direct ionization is described by configuration-averaged distorted-wave theory and indirect ionization by $R$-matrix theory. Indirect processes contribute to the total ionization cross section by up to $\ensuremath{\sim}40%$. This finding is related to the existence of strong $3p\ensuremath{\rightarrow}3d$ excitation channels in ${\mathrm{Sc}}^{+}(3{p}^{6}3d4s)$. The shape of the related cross-section feature is reminiscent of the very strong $4d\ensuremath{\rightarrow}4f$ excitation, found in the ionization of xenon and its neighboring elements.

Electron-impact ionization cross sections for helium are calculated using time-dependent close-coupling theory. The total wave function for the three electron system is expanded in nine dimensions, where three dimensions are represented on a radial lattice and a coupled channels expansion is used to represent the other six dimensions. Collision cross sections are obtained by t{yields}{infinity} projection onto fully antisymmetric spatial and spin functions, with care as to orthogonality of different representations. Cross sections are also obtained using time-independent first- and second-order perturbative distorted-wave theory. Total cross sections are calculated at incident energies above the double ionization threshold for electron-impact single ionization leaving He{sup +} in the 1s, 2s, and 2p states and for electron-impact double ionization. Both the single ionization cross section, leaving He{sup +} in the 1s ground state, and the double ionization cross section are in excellent agreement with previous absolute experimental measurements.

The time-dependent close-coupling theory is extended to allow the calculation of e-H elastic and inelastic scattering processes. We first calculate {sup 1,3}S elastic scattering cross sections for H(1s) in time-dependent Hartree-Fock theory and find good agreement with time-independent distorted-wave theory. We then calculate elastic scattering cross sections for H(1s) using time-dependent close-coupling theory and find good agreement with R-matrix scattering theory. Finally, we apply the time-dependent close-coupling method to calculate elastic and inelastic cross sections for H(2s) and H(2p). Correlation effects are found to be important in all elastic and inelastic processes involving the n=2 excited states of hydrogen. In particular, the ionization cross sections are used to calculate ionization rate coefficients for comparison with rate coefficients currently used in collisional-radiative models.

The time-dependent close-coupling method is used to calculate electron-impact excitation cross sections for the Li(2s){yields}Li(nl) and Li(2p){yields}Li(nl) transitions at incident energies just above the ionization threshold. The implementation of the time-dependent close-coupling method on a nonuniform lattice allows the study of continuum-coupling effects in excitations to high principal quantum number, i.e., n{

Excitation and ionization cross sections are calculated for e-He{sup +} scattering at electron impact energies of 100, 200, and 300 eV, using a time-dependent close-coupling method that employs variable lattice spacings. The He{sup +} ionization cross section is found to be in good agreement with previous converged close-coupling calculations and experimental measurements. Excitation cross sections for 1s{yields}ns,np transitions in He{sup +} are presented for high n values well beyond the reach of available experimental measurements and previous nonperturbative theories. The relative difference between the nonperturbative close-coupling and the perturbative distorted-wave results is found to grow larger as the principal quantum number n is increased. This difference has important implications in the collisional-radiative modeling of many astrophysical and laboratory plasmas that use perturbation theory.

In the published version of this paper, there are some minor inaccuracies in the absorption-line wavelengths listed in Table 4 as a result of a faulty reduction procedure of the Obs6615 spectrum. The shifts have been detected in a comparison with the wavelengths listed for this spectrum in the Chandra Transmission Grating Catalog and Archive (TGCat8). They are due to incorrect centroid positions of the zero-order image in both reductions as determined by the tgdetect utility which, when disentangled, yield the improved line positions of the amended Table 4 given below. It must also be pointed out that other quantitative findings of the original paper: 1. Table 5, p. 9: the column density (NH), ionization parameter, oxygen abundance of the warmabs model and the normalization and photon index of the power-law model; 2. Table 6, p. 9: the hydrogen column density of the warmabs fit; 3. Table 7, p. 9: the present oxygen equivalent widths of XTE J1817-330; and 4. Table 8, p. 10: the present oxygen column densities of XTE J1817-330 derived from both the curve of growth and warmabs model fit have been revised in the new light and are, within the estimated uncertainty ranges, in good accord with the new rendering.

Complete data sets of level energies, transition wavelengths, A-values, radiative and Auger widths and fluorescence yields for K-vacancy levels of the F, Na, P, Cl, K, Sc, Ti, V, Cr, Mn, Co, Cu and Zn isonuclear sequences have been computed by a Hartree-Fock method that includes relativistic corrections as implemented in Cowan's atomic structure computer suite. The atomic parameters for more than 3 million fine-structure K lines have been determined. Ions with electron number N greater than 9 are treated for the first time, and detailed comparisons with available measurements and theoretical data for ions with N less than or equal to 9 are carried out in order to estimate reliable accuracy ratings.

We present multi-configuration Breit-Pauli distorted-wave photoionization (PI) cross sections and radiative recombination (RR) and dielectronic recombination (DR) rate coefficients for the first six krypton ions. These were calculated with the AUTOSTRUCTURE code, using semi-relativistic radial wavefunctions in intermediate coupling. Kr has been detected in several planetary nebulae (PNe) and H II regions, and is a useful tracer of neutron-capture nucleosynthesis. PI, RR, and DR data are required to accurately correct for unobserved Kr ions in ionized nebulae, and hence to determine elemental Kr abundances. PI cross sections have been determined for ground configuration states of Kr^0--Kr^5+ up to 100 Rydbergs. Our Kr^+ PI calculations were significantly improved through comparison with experimental measurements. RR and DR rate coefficients were determined from the direct and resonant PI cross sections at temperatures (10^1--10^7)z^2 K, where z is the charge. We account for Delta n=0 DR core excitations, and find that DR is the dominant recombination mechanism for all but Kr^+ at photoionized plasma temperatures. Internal uncertainties are estimated by comparing results computed with three different configuration-interaction expansions for each ion, and by testing the sensitivity to variations in the orbital radial scaling parameters. The PI cross sections are generally uncertain by 30-50% near the ground state thresholds. Near 10^4 K, the RR rate coefficients are typically uncertain by, 19 pages, 8 figures. Accepted for publication in Astronomy & Astrophysics

We investigate the absorption structure of the oxygen in the interstellar medium by analyzing {\it XMM}-Newton observations of the low mass X-ray binary Sco X-1. We use simple models based on the O {\sc i} atomic cross section from different sources to fit the data and evaluate the impact of the atomic data in the interpretation of astrophysical observations. We show that relatively small differences in the atomic calculations can yield spurious results. We also show that the most complete and accurate set of atomic cross sections successfully reproduce the observed data in the $21-24.5$ {\AA} wavelength region of the spectrum. Our fits indicate that the absorption is mainly due to neutral gas with an ionization parameter of $\xi=10^{-4}$ erg cm s$^{-1}$, and an oxygen column density of $N_{\mathrm{O}}\approx 8-10\times 10^{17}$ cm$^{-2}$. Our models are able to reproduce both the K edge and the K$\alpha$ absorption line from O {\sc i}, which are the two main features in this region. We find no conclusive evidence for absorption by other than atomic oxygen., Comment: 15 pages, 4 figures, 1 table. Accepted for publication in ApJ Letters

Context. Accurate atomic data for the less abundance Fe-peak elements are required for use in X-ray astrophysical studies. Aims. We calculate high quality electron-impact excitation collision strengths and effective collision strengths for hydrogenic Cr, Mn, Fe, Co, and Ni. Methods. We use the Dirac R-matrix method, the intermediate coupling frame transformation R-matrix method, the semi-relativistic distorted-wave method and the fully-relativistic distorted-wave method to calculate collision strengths for each of the ions. The ADAS collisional-radiative codes are used to produce photon emissivity coefficients for each ion. Results. Results are presented for atomic energy levels, spontaneous emission coefficients, electron-impact excitation collision strengths and associated effective collision strengths for each of the five species under consideration. We find relativistic effects can contribute an approximate 10% increase to the background cross section in relation to semi-relativistic collision calculations. We also confirm that radiation damping plays a prominent role for certain near threshold resonances. In order check the integration of our results within collisional-radiative modeling codes, we have used the ADAS package for some preliminary modeling of photon emissivities. The atomic data shall be made available online through the OPEN-ADAS site and the CFADC database

Radiative and Auger decay data have been calculated for modeling the K lines of the aluminum isonuclear sequence, from Al 0 up to Al 11+ . Level energies, transition wavelengths, radiative transition probabilities, and radiative and Auger widths were determined using Cowan’s Hartree-Fock with relativistic corrections (HFR) method. Results are compared with data sets computed with the AUTOSTRUCTURE and GRASP atomic structure codes and with available experimental and theoretical values, mainly in highly ionized ions and in the solid state.

We report on our progress in understanding the dynamics of atomic and molecular collision processes using time-dependent close-coupling methods