Transition Probabilities For Ions Research Articles

AtomPy: An Open Atomic Data Curation Environment for Astrophysical Applications

We present a cloud-computing environment, referred to as AtomPy, based on Google-Drive Sheets and Pandas (Python Data Analysis Library) DataFrames to promote community-driven curation of atomic data for astrophysical applications, a stage beyond database development. The atomic model for each ionic species is contained in a multi-sheet workbook, tabulating representative sets of energy levels, A-values and electron impact effective collision strengths from different sources. The relevant issues that AtomPy intends to address are: (i) data quality by allowing open access to both data producers and users; (ii) comparisons of different datasets to facilitate accuracy assessments; (iii) downloading to local data structures (i.e., Pandas DataFrames) for further manipulation and analysis by prospective users; and (iv) data preservation by avoiding the discard of outdated sets. Data processing workflows are implemented by means of IPython Notebooks, and collaborative software developments are encouraged and managed within the GitHub social network. The facilities of AtomPy are illustrated with the critical assessment of the transition probabilities for ions in the hydrogen and helium isoelectronic sequences with atomic number Z ≤ 10.

Radiative transition probabilities in ions of the silver isoelectronic sequence

The wave functions of one-electron states above the 4d10 core have been calculated within the relativistic perturbation theory with a zero-order model potential. The wavelengths and probabilities of electric dipole transitions in an Ag-like ion have been calculated for the 5s-5p, 5p-5d, 5d-5f, and 4f-5d transitions. The data obtained are compared with the results of calculations by the relativistic Hartree-Fock method and within the relativistic many-body perturbation theory. The theoretical results are compared with experimental data on the lifetimes of energy levels in Ag-like ions.

E2 and M1 Transition Probabilities in Ions of the Nitrogen Isoelectronic Sequence Calculated using MBPT

Forbidden electric quadrupole (E2) and magnetic dipole (M1) transitions are of extreme importance in astrophysics. Up to now the most extensive calculations for the nitrogen isoelectronic sequence have been done using the method proposed by C.J. Zeippen [1] or in MCHF approximation [2]. To account for electron correlations both these methods use a large list of configurations. We have chosen the stationary many-body perturbation theory (MBPT) [3] for the inclusion of the electron correlations. The calculations have been perfomed in the second order in the complete model space 1s22s2p3+ 1s22p5. Relativistic corrections have been accounted for in the Breit-Pauli approximation. In the Table we present probabilities for electric quadrupole W(E2) and magnetic dipole W(M1) transitions (in s−1), wavelengths λ (in A). The comparision of the results shows that our second order calculation data in the most cases are closer to term-energy corrected ones from [1].

Accurate transition probabilities in ions obtained by isoelectronic smoothing of line strengths.

Lifetime measurements, based on the method of beam-foil spectroscopy, together with careful corrections for cascade effects, have in recent years yielded the line strength of the 2s2 1S-2s2p 1P°transition in Be-like ions with uncertainties ranging from 3.4% to 8.1% in Bei-O. By applying a method of isoelectronic smoothing of line strengths, similar to those earlier used for excitation energies and transition wavelengths, we have reduced the experimental uncertainties by about a factor of 2, to 1.9-3.6 % for these transitions. The fitted results are in excellent agreement with the best theoretical data. The applicability of this method to other isoelectronic sequences is briefly discussed.

Calculated term energies and transition probabilities for ions in the fluorine isoelectronic sequence

Calculations are presented of intermediate-coupling energies for levels of the complex (12 26 31) and probabilities for permitted transitions from these levels to the levels of the ground configuration in the fluorine-like ions Sc xiii, Fe xviii, and Cu xxi.