Sextet transitions in Fe ii

We have calculated oscillator strengths for the J – J ' levels of the a  ⁶D– z  ⁶P^o, the a  ⁶D– z  ⁶D^o and the a  ⁶D– z  ⁶F^o multiplets in Fe  ii , using configuration interaction wave functions. The importance of the mixing of the ⁶P^o, ⁶D^o and ⁶F^o states is shown, as is the effect of core polarization of both the 3 p and 3 s orbitals. Good agreement with recent experimental results is obtained.     

Core-polarization effects, oscillator strengths and radiative lifetimes of levels in Pb iii

Transition probabilities and oscillator strengths of 382 lines with astrophysical interest arising from 5d⁹6s²6p, 5d¹⁰6s n l, 5d¹⁰6s², 5d¹⁰6p², 5d¹⁰6p7s and 5d¹⁰6p6d configurations and some levels radiative lifetimes of Pb  iii have been calculated. These values were obtained in intermediate coupling (IC) and using relativistic Hartree–Fock calculations including core-polarization effects. We use for the IC calculations the standard method of least-square fitting from experimental energy levels by means of Cowan computer code. The inclusion in these calculations of the 5d¹⁰6p7s and 5d¹⁰6p6d configurations has facilitated us a complete assignment of the levels of energy in the Pb  iii . Transition probabilities, oscillator strengths and radiative lifetimes obtained are generally in good agreement with the experimental data.     

Inner-shell photoionization of O iii

A 25-state R -matrix calculation is performed to obtain photoionization cross-sections for transitions from the 1s²2s²2p²³P ground state of the O  iii ion. Results are obtained for a range of photon energies, including those at which K-shell photoionization processes take place. We compare our results with those from previous calculations. Excellent agreement is obtained. We also consider resonances owing to transitions of a 1s electron excited into the 2p orbital and compare with a recent calculation.     

Experimental and theoretical studies of Dy iii: radiative lifetimes and oscillator strengths of astrophysical interest

The lifetimes of three short-lived levels belonging to the 4f⁹6p configuration and of two long-lived levels of the 4f⁹5d configuration of Dy  iii have been measured for the first time using time-resolved laser-induced fluorescence techniques. They are in good agreement with theoretical values calculated within the framework of a pseudo-relativistic configuration interaction approximation. Using the experimental lifetimes and the theoretical branching fractions, a first set of transition probabilities of astrophysical interest has been obtained for Dy  iii .     

Oscillator strengths for optically allowed transitions in carbon-like ions

Using configuration interaction wavefunctions, the excitation thresholds for the twelve lowest terms arising from the configurations 1s ²2s ²2p ², 1s ²2s2p ³, and 1s ²2p ⁴ of Mgvii have been calculated. The same wavefunctions have been used to calculate the oscillator strengths for the optically allowed transitions in Mgvii. Combining these results with earlier published values for Oiii, Nev, Siix, Caxv, and Fexxi, oscillator strengths for other ions in the carbon isoelectronic sequence (F through Ni) have been predicted. The predicted values are found to be slightly lower when compared with the available published results.     

Experimental and theoretical radiative lifetimes, branching fractions and oscillator strengths in Lu iiii

By a combination of radiative lifetimes measured using the fast-beam-laser method and experimental branching ratios deduced from Fourier transform spectrometer spectra, it has been possible to derive experimental f -values for Lu  ii lines observed in the visible and near-ultraviolet regions. These data are compared with relativistic Hartree–Fock calculations, taking core polarization effects into account, and a set of additional oscillator strengths of astrophysical interest is presented.     

Emission lines of Fe xv in spectra obtained with the Solar Extreme-Ultraviolet Research Telescope and Spectrograph

Recent R-matrix calculations of electron impact excitation rates in Mg-like Fe  xv are used to derive theoretical emission-line ratios involving transitions in the 243–418 Å  wavelength range. A comparison of these with a data set of solar active region, subflare and off-limb spectra, obtained during rocket flights by the Solar Extreme-Ultraviolet Research Telescope and Spectrograph (SERTS), reveals generally very good agreement between theory and observation, indicating that most of the Fe  xv emission lines may be employed with confidence as electron density diagnostics. In particular, the 312.55-Å  line of Fe  xv is not significantly blended with a Co  xvii transition in active region spectra, as suggested previously, although the latter does make a major contribution in the subflare observations. Most of the Fe  xv transitions which are blended have had the species responsible clearly identified, although there remain a few instances where this has not been possible. We briefly address the long-standing discrepancy between theory and experiment for the intensity ratio of the  3s^2 1S–3s3p ³P₁  intercombination line at 417.25 Å  to the  3s^2 1S–3s3p ¹P  resonance transition at 284.16 Å.     

类氖铁(Fe XVII)离子能级及振子强度计算

利用原子数据模拟程序RCN／RCG、AUTOSTRUCTURE(AS)、GRASP分别对类氖铁的离子结构进行计算，计算过程包含了对波函数的相对论修正，计算结果包括电偶级光谱跃迁的能级间隔，谐振子强度，跃迁几率，并与实验值进行了比较，分析了3种原子数据模拟程序在计算原子结构上的精确度．