New X-ray observatories (Chandra and XMM-Newton) are providing a wealth of high-resolution X-ray spectra in which hydrogen- and helium-like ions are usually strong features. We present results from a new collisional-radiative plasma code, the Astrophysical Plasma Emission Code (APEC), which uses atomic data in the companion Astrophysical Plasma Emission Database (APED) to calculate spectral models for hot plasmas. APED contains the requisite atomic data such as collisional and radiative rates, recombination cross sections, dielectronic recombination rates, and satellite line wavelengths. We compare the APEC results to other plasma codes for hydrogen- and helium-like diagnostics and test the sensitivity of our results to the number of levels included in the models. We find that dielectronic recombination with hydrogen-like ions into high (n = 6-10) principal quantum numbers affects some helium-like line ratios from low-lying (n = 2) transitions.

https://iopscience.iop.org/article/10.1086/322992/pdf

Collisional Plasma Models with APEC/APED: Emission-Line Diagnostics of Hydrogen-like and Helium-like Ions

We describe a complete software package for the computation of various atomic data such as energy levels; radiative transition; collisional excitation; ionization by electron impact, photoionizatio...

The flexible atomic code

We describe the latest release of AtomDB, version 2.0.2, a database of atomic data and a plasma modeling code with a focus on X-ray astronomy. This release includes several major updates to the fundamental atomic structure and process data held within AtomDB, incorporating new ionization balance data, state-selective recombination data, and updated collisional excitation data for many ions, including the iron L-shell ions from Fe+16 to Fe+23 and all of the hydrogen- and helium-like sequences. We also describe some of the effects that these changes have on calculated emission and diagnostic line ratios, such as changes in the temperature implied by the He-like G-ratios of up to a factor of two.

https://iopscience.iop.org/article/10.1088/0004-637X/756/2/128/pdf

Updated Atomic Data and Calculations for X-Ray Spectroscopy

We describe H ULLAC , an integrated code for calculating atomic structure and cross sections for collisional and radiative atomic processes. This code evolved and has been used over the years, but so far, there was no coherent, comprehensive, and in-depth presentation of it. It is based on relativistic quantum mechanical calculations including configuration interaction. The collisional cross sections are calculated in the distorted wave approximation. The theory and code are presented, emphasizing the various novel methods that has been developed to obtain accurate results very efficiently. In particular we describe the parametric potential method used for both bound and free orbitals, the factorization–interpolation method applied in the derivation of collisional rates, the phase amplitude approach for calculating the continuum orbitals and the N JGRAF graphical method used in the calculation of the angular momentum part of the matrix elements. Special effort has been made to insure the simplicity of use, which is demonstrated in an example.

HULLAC, an integrated computer package for atomic processes in plasmas

We describe the latest release of AtomDB, version 2.0.2, a database of atomic data and a plasma modeling code with a focus on X-ray astronomy. This release includes several major updates to the fundamental atomic structure and process data held within AtomDB, incorporating new ionization balance data, state-selective recombination data, and updated collisional excitation data for many ions, including the iron L-shell ions from Fe$^{+16}$ to Fe$^{+23}$ and all of the hydrogen- and helium-like sequences. We also describe some of the effects that these changes have on calculated emission and diagnostic line ratios, such as changes in the temperature implied by the He-like G-ratios of up to a factor of 2.

Updated Atomic Data and Calculations for X-ray Spectroscopy

Measurements of the fine structure on the high-energy side of the Fe Kβ x-ray line, obtained from low-inductance high-current vacuum sparks, are reported. Fully relativistic central field calculations for atoms, including magnetic Breit interactions and estimates of the Lamb shifts, correlate the experimental features to the 1s-3p transition of the various Fe ions. The features are shown to be emitted by ions from Fe ix to Fe xviii, and Fe xxiv to Fe xxvi.

The 1s-3p Kβ-like x-ray spectrum of highly ionized iron

The spectra of elements Y, Zr, Nb, Mo, Ru, Rh, Pd, and Ag in the 10–100-A range were obtained from a high-power vacuum spark and a grazing-incidence high-resolution spectrograph. The transitions 3d10–3d94p, 3d10–3d94f, 3d10–3d95p, and 3d10–3d95f were identified. The agreement with ab initio relativistic calculations is good. The relevance of the jj coupling scheme for level labeling is discussed, as is the importance of relativistic effects, by comparing the scheme with other results on high-Z atoms (up to Pt).

B. S. Fraenkel

Papers

The 1s-3p Kβ-like x-ray spectrum of highly ionized iron

Nickel-like spectra of elements Y xii to Ag xx from a vacuum spark