P-like Ions Research Articles

Energy and transition data computations for P-like ions: As, Kr, Sr, Zr, Mo, and W

The multiconfiguration Dirac–Hartree–Fock (MCDHF) and relativistic configuration interaction (RCI) methods were used to compute excitation energies and transition data for the 147 lowest states of the even 3s3p4, 3s23p23d, 3p43d, 3s3p23d2 configurations and for the 124 lowest states of the odd 3s23p3, 3p5, 3s3p33d, 3s23p3d2, 3p33d2 configurations for the P-like ions: As XIX, Kr XXII, Sr XXIV, Zr XXVI, Mo XXVIII, and W LX. E1 transition rates and weighted oscillator strengths among these states are given. Valence–valence, core–valence and core–core electron correlation effects are included. Computed excitation energies and transition data are compared with the NIST recommended values and experimental or theoretical results of other authors. All calculations were performed using the general relativistic atomic structure package GRASP2018.

Atomic Data Assessment with PyNeb

PyNeb is a Python package widely used to model emission lines in gaseous nebulae. We take advantage of its object-oriented architecture, class methods, and historical atomic database to structure a practical environment for atomic data assessment. Our aim is to reduce the uncertainties in the parameter space (line ratio diagnostics, electron density and temperature, and ionic abundances) arising from the underlying atomic data by critically selecting the PyNeb default datasets. We evaluate the questioned radiative-rate accuracy of the collisionally excited forbidden lines of the N- and P-like ions (O ii, Ne iv, S ii, Cl iii, and Ar iv), which are used as density diagnostics. With the aid of observed line ratios in the dense NGC 7027 planetary nebula and careful data analysis, we arrive at emissivity ratio uncertainties from the radiative rates within 10%, a considerable improvement over a previously predicted 50%. We also examine the accuracy of an extensive dataset of electron-impact effective collision strengths for the carbon isoelectronic sequence recently published. By estimating the impact of the new data on the pivotal [N ii] and [O iii] temperature diagnostics and by benchmarking the collision strength with a measured resonance position, we question their usefulness in nebular modeling. We confirm that the effective-collision-strength scatter of selected datasets for these two ions does not lead to uncertainties in the temperature diagnostics larger than 10%.

Large-scale Multiconfiguration Dirac–Hartree–Fock Calculations for Astrophysics: n = 4 Levels in P-like Ions from Mn xi to Ni xiv

Using the multiconfiguration Dirac-Hartree-Fock and the relativistic configuration interaction methods, a consistent set of transition energies and radiative transition data for the lowest 546 (623, 701, 745) states of the $3p^4 3d$, $3s 3p^2 3d^2$, $3s 3p^3 4p$, $3s 3p^4$, $3s^2 3d^3$, $3s^2 3p^2 3d$, $3s^2 3p^2 4d$, $3s^2 3p^2 4s$, $3p^3 3d^2$, $3p^5$, $3s 3p 3d^3$, $3s 3p^3 3d$, $3s 3p^3 4s$, $3s^2 3p 3d^2$, %$3s^2 3p^2 4f$, $3s^2 3p^2 4p$, $3s^2 3p^3$ configurations in Mn~XI (Fe~XII, Co~XIII, Ni~XIV) is provided. The comparison between calculated excitation energies for the $n=4$ states and available experimental values for Fe XII indicate that the calculations are highly accurate, with uncertainties of only a few hundred cm$^{-1}$. Lines from these states are prominent in the soft X-rays. With the present calculations, several recent new identifications are confirmed. Other identifications involving $3p^2 4d$ levels in Fe~XII that were found questionable are discussed and a few new assignments are recommended. As some $n=4$ states of the other ions also show large discrepancies between experimental and calculated energies, we reassess their identification. The present study provides highly accurate atomic data for the $n=4$ states of P-like ions of astrophysical interest, for which experimental data are scarce.

Energy Levels, Lifetimes, and Transition Rates for P-like Ions from Cr x to Zn xvi from Large-scale Relativistic Multiconfiguration Calculations

Abstract The fully relativistic multiconfiguration Dirac–Hartree–Fock method is used to compute excitation energies and lifetimes for the 143 lowest states of the , 3s3p 4, , 3s3p 33d, 3p 5, configurations in P-like ions from Cr x to Zn xvi. Multipole (E1, M1, E2, M2) transition rates, line strengths, oscillator strengths, and branching fractions among these states are also given. Valence–valence and core–valence electron correlation effects are systematically accounted for using large basis function expansions. Computed excitation energies are compared with the NIST ASD and CHIANTI compiled values and previous calculations. The mean average absolute difference, removing obvious outliers, between computed and observed energies for the 41 lowest identified levels in Fe xii, is only 0.057%, implying that the computed energies are accurate enough to aid identification of new emission lines from the Sun and other astrophysical sources. The amount of energy and transition data of high accuracy are significantly increased for several P-like ions of astrophysics interest, where experimental data are still very scarce.

Relativistic many-body Møller–Plesset perturbation theory calculations of the energy levels and transition rates in Na-like to P-like Xe ions

Relativistic multireference many-body perturbation theory calculations have been performed for Xe 43+ to Xe 39+ ions, resulting in energy levels, electric dipole transition rates, and level lifetimes. The second-order many-body perturbation theory calculation of energy levels included mass shifts, the frequency-dependent Breit correction, and Lamb shifts. The calculated transition energies and E1 transition rates are used to present synthetic spectra in the extreme ultraviolet range for some of the Xe ions.

Relativistic multireference many-body perturbation theory calculations on Au64+ - Au69+ ions

Many-body perturbation theory (MBPT) calculations are an adequate tool for the description of the structure of highly charged multi-electron ions and for the analysis of their spectra. We demonstrate this by way of a re-investigation of n=3, Δn=0 transitions in the EUV spectra of Na-, Mg-, Al-like, and Si-like ions of Au that have been obtained previously by heavy-ion accelerator based beam-foil spectroscopy. We discuss the evidence and propose several revisions on the basis of our multi-reference many-body perturbation theory calculations of Ne- through P-like ions of Au.

Relativistic multireference many-body perturbation theory calculations on F-, Ne-, Na-, Mg-, Al-, Si- and P-like xenon ions

Many-body perturbation theory (MBPT) has been employed to calculate with high wavelength accuracy the extreme ultraviolet (EUV) spectra of F-like to P-like Xe ions. We discuss the reliability of the new calculations using the example of EUV beam–foil spectra of Xe, in which n = 3, Δn = 0 transitions of Na-, Mg-, Al- and Si-like ions have been found to dominate. A further comparison is made with spectra from an electron beam ion trap, that is, from a device with a very different (low density) excitation balance.

Soft-x-ray spectra of highly charged Kr ions in an electron beam ion trap.

Systematic variation of the electron-beam energy in the EBIT-II electron beam ion trap has been employed to produce soft-x-ray spectra (20-75 A) of Kr with well-defined maximum charge states ranging from Cu- to Al-like ions. Guided by large-scale relativistic atomic structure calculations, the strongest lines have been identified with Delta n=1 (n=3 to n(')=4) transitions from Ni- to P-like ions (Kr(8+)-Kr(21+)), as well as a number of 3p-4d and 3d-5f transitions.

ExperimentalM1transition rates in highly charged Kr ions

Atomic level lifetimes have been measured on magnetic dipole $(M1)$ transitions in Si-like, P-like, Ar-like, K-like, and Ca-like ions of Kr, using an electron-beam ion trap in magnetic trapping mode. The lifetimes are compared to various predictions, including the results of different calculations. In Ar-like ions, magnetic quadrupole $(M2)$ transitions have been identified as significant competing decay channels.

Crossed-beams measurements of absolute cross sections for electron impact ionization of S +

Absolute cross sections for electron impact ionization of S + have been measured in the electron energy range from 30-250 eV using the crossed-beams technique. Results are compared with sealed cross sections from other P-like ions, with a semiempirical formula and with other recently reported measurements. Expansion coefficients and formulas for generating ionization rate coefficients in the electron temperature range 10 4 K ⩽ T ⩽ 10 6 K are presented.