Ag-like Ions Research Articles

Analysis of E3 Transitions in Ag-like High-Z Ions Observed with the NIST EBIT

We report measurements and identification of the E3 4f7/2,5/2-5s1/2 transitions and E1 allowed transitions in Ag-like W (Z = 74), Re (Z = 75), and Ir (Z = 77). The spectra were recorded at the NIST EBIT using a grazing-incidence EUV spectrometer. The present measured wavelengths and theoretical predictions using GRASP2K calculations confirm previous observations of the same E3 transitions in Ag-like W. Our collisional–radiative model using the NOMAD code offers an insight into the population kinematics for Ag-like ions of heavy elements. We discuss the observed spectra and comparisons of the measured and simulated spectral lines.

M1 transition energy and rate in the ground configuration of Ag-like ions with 62 ⩽ Z ⩽ 94

Systematic calculations and assessments are performed for the magnetic dipole (M1) transition energies and rates between the levels in the ground configuration 4d104f along the Ag-like isoelectronic sequence with 62 ⩽ Z ⩽ 94 based on the second-order many-body perturbation theory implemented in the Flexible Atomic Code. The electron correlations, Breit interaction and quantum electrodynamics effects are taken into account in the present calculations. The accuracy and reliability of our results are evaluated through comprehensive comparisons with available measurements and other theoretical results. For transition energies, our results are in good agreement with the recent experimental data obtained from the electron beam ion traps within 0.18%. The maximum discrepancy between our results and those obtained with the large-scale multiconfiguration Dirac–Hartee–Fock calculations by Grumer et al. [Phys. Rev. A 89 062501 (2014)] is less than 0.13% along the isoelectronic sequence. Furthermore, the corresponding M1 transition rates are also reported. The present results can be used as the benchmark and useful for spectra simulation and diagnostics of astrophysical and fusion plasmas.

Systematic Observation of EUV Spectra from Highly Charged Lanthanide Ions in the Large Helical Device

We have systematically observed extreme ultraviolet (EUV) spectra from highly charged ions of nine lanthanide elements with atomic numbers from 60–70 in optically thin plasmas produced in the Large Helical Device (LHD). Discrete spectral features with isolated lines from relatively higher charge states around Cu-like ions are observed under high temperature conditions around 2 keV, while narrowed quasicontinuum features from charge states around Ag-like ions are observed under low temperature conditions below 1 keV. The positions of the lines and the quasicontinuum features systematically move to shorter wavelengths as the atomic number increases. The wavelengths of the main peaks in the quasicontinuum features agree well with those of singlet transitions of Pd-like ions reported previously. We have easily identified discrete spectral lines from Cu-like and Ag-like ions, some of which are experimentally identified for the first time in the LHD. Their wavelengths are compared with theoretical calculations using a GRASP family of atomic codes. The theoretical values are synthesized to the LHD experimental data for the cases of Ag- and Pd-like ions.

Visible transitions in Ag-like and Cd-like lanthanide ions

We present visible spectra of Ag-like ($4d^{10}4f$) and Cd-like ($4d^{10}4f^2$) ions of Ho (atomic number $Z=67$), Er (68), and Tm (69) observed with a compact electron beam ion trap. For Ag-like ions, prominent emission corresponding to the M1 transitions between the ground state fine structure splitting $4f_{5/2}$--$4f_{7/2}$ is identified. For Cd-like ions, several M1 transitions in the ground state configuration are identified. The transition wavelength and the transition probability are calculated with the relativistic many-body perturbation theory and the relativistic CI + all-order approach. Comparisons between the experiments and the calculations show good agreement.

Temperature dependent EUV spectra of Gd, Tb and Dy ions observed in the Large Helical Device

We have observed a number of different types of extreme ultraviolet (EUV) spectra from highly charged gadolinium (Gd), terbium (Tb) and dysprosium (Dy) ions in optically thin plasmas produced in the Large Helical Device at the National Institute for Fusion Science. Temporal changes in EUV spectra in the 6–9 nm region subsequent to the injections of solid pellets were measured by a grazing incidence spectrometer. The spectra rapidly change from discrete features into unresolved transition arrays (UTAs) following a drop in the electron temperature after the heating power is reduced. In particular, extremely narrowed UTA features, which comprise spectral lines of Ag-like, Pd-like and neighboring ion stages, are observed when the peak electron temperature is less than 0.45 keV due to the formation of hollow plasmas. Some discrete spectral lines of Cu-like and Ag-like ions have been identified in the high and low temperature plasmas, respectively, some of which are experimentally identified for the first time.

Coronal lines and the importance of deep-core–valence correlation in Ag-like ions

We report on large-scale and critically evaluated {\em ab initio} MCDHF calculations of the wavelength of the "coronal", M1 transition $4f\ ^2\mathrm{F}_{5/2}^o-^2\mathrm{F}_{7/2}^o$ in Ag-like ions. The transition between these two fine structure levels, which makes up the ground term for $Z \ge 62$ in the isoelectronic sequence, has recently been observed in Yb$^{23+}$ and W$^{27+}$, where the latter could be of great importance for fusion plasma diagnostics. We present recommended values for all members of the sequence between $Z = 50$ and $94$, which are supported by excellent agreement with values from recent experiments. The importance of including core-valence correlation with the $n=3$ shell in the theoretical model is emphasized. The results show close to spectroscopic accuracy for these forbidden lines.

M1 transition energies and probabilities between the multiplets of the ground state of Ag-like ions with Z = 47–92

Extensive relativistic configuration interaction calculations have been performed for the 4d104f and 4d105s states of the Ag-like isoelectronic ion using the GRASP2K package based on the multi-configuration Dirac–Fock method. The active space techniques have been employed to extend the configuration expansion systematically. The electron correlation effects, Breit interaction and quantum electrodynamics effects to the atomic state wavefunctions and the corresponding energies have been taken into account. Good agreement has been obtained in a general trend with the existing experimental and theoretical values. The change of the ground state configuration from 4d105s to 4d104f is predicted to occur at Z = 62. The transition energy and probability of the M1 transition between the 4d104f multiplets are, respectively, scaled to be 0.01(Z*)4 cm−1 and 1.95 × 10−17(Z*)11.97 s−1, where Z* = Z − 34.42 is the effective nuclear charge number for Ag-like ions with Z ⩾ 62. Our results show the need for more high-precision experiments for Z ⩾ 68 ions.

Transition probabilities for 5s–5p, 5p–5d, 4f–5d, and 5d–5f transitions in Ag-like ions with Z = 50–86

The wavelengths, electric dipole transition probabilities, and oscillator strengths are calculated for transitions between low-lying states (5s–5p, 5p–5d, 4f–5d, and 5d–5f) in the silver isoelectronic sequence (50 ⩽ Z ⩽ 86) using relativistic perturbation theory with a zero-approximation model potential. The results are compared with the corresponding data of the relativistic Hartree–Fock theory and the relativistic many-body perturbation theory. The results of these three theoretical approaches are compared with available experimental data for the level lifetimes. Possible reasons for some disagreements are discussed.

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.

Relativistic many-body calculations of excitation energies and transition rates from core-excited states in silverlike ions

Energies of [Kr]4d94f2, [Kr]4d94f5l, and [Kr]4d95l5l′ states (with l = s, p, d, f) for Ag-like ions with Z = 50–100 are evaluated to second order in relativistic many-body perturbation theory (RMBPT) starting from a Pd-like Dirac–Fock potential ([Kr]4d10). Second-order Coulomb and Breit–Coulomb interactions are included. Correction for the frequency dependence of the Breit interaction is taken into account in lowest order. The Lamb-shift correction to energies is also included in lowest order. Intrinsic particle–particle–hole contributions to energies are found to be 20–30% of the sum of the one- and two-body contributions. Transition rates and line strengths are calculated for the 4d–4f and 4d–5l electric-dipole (E1) transitions in Ag-like ions with nuclear charge Z = 50–100. RMBPT including the Breit interaction is used to evaluate retarded E1 matrix elements in length and velocity forms. First-order RMBPT is used to obtain intermediate coupling coefficients and second-order RMBPT is used to calculate transition matrix elements. A detailed discussion of the various contributions to the dipole matrix elements and energy levels is given for silverlike tungsten (Z = 74). The transition energies included in the calculation of oscillator strengths and transition rates are from second-order RMBPT. Trends of the transition rates as functions of Z are illustrated graphically for selected transitions. Additionally, we perform calculations of energies and transition rates for Ag-like W by the Hartree–Fock relativistic method (Cowan code) and the Multiconfiguration Relativistic Hebrew University Lawrence Atomic Code (HULLAC code) to compare with results from the RMBPT code. These atomic data are important in modeling of N-shell radiation spectra of heavy ions generated in various collision as well as plasma experiments. The tungsten data are particularly important for fusion application.PACS Nos.: 31.15.A–, 31.15.ag, 31.15.am, 31.15.aj

Third-order relativistic many-body calculations of energies and lifetimes of levels along the silver isoelectronic sequence

Energies of ${5l}_{j}(l=s,p,d,f,g)$ and ${4f}_{j}$ states in neutral Ag and Ag-like ions with nuclear charges $Z=48--100$ are calculated using relativistic many-body perturbation theory. Reduced matrix elements, oscillator strengths, transition rates, and lifetimes are calculated for the 17 possible ${5l}_{j}\ensuremath{-}{5l}_{{j}^{\ensuremath{'}}}^{\ensuremath{'}}$ and ${4f}_{j}\ensuremath{-}{5l}_{{j}^{\ensuremath{'}}}$ electric-dipole transitions. Third-order corrections to energies and dipole matrix elements are included for neutral Ag and for ions with $Z<~60.$ Second-order corrections are included for $Z>60.$ Comparisons are made with available experimental data for transition energies and lifetimes. Correlation energies and transition rates are shown graphically as functions of nuclear charge Z for selected cases. These calculations provide a theoretical benchmark for comparison with experiment and theory.

Excitation energies and oscillator strengths in the silver isoelectronic sequence

Excitation energies and oscillator strengths for electric dipole transitions between low-lying states in the silver isoelectronic sequence are studied using relativistic Hartree-Fock wave functions. For Z ≥ 61, our calculation shows that the ground state of Ag-like ions is 4f2F5/2 rather than 5s 2S1/2. We found a diminishing role of the spin-orbit effect on transitions between levels with high angular momenta. Effects of anticrossings between 4d9 4f2 and 4d10 5l (l = 0,2,4) states at high Z are discussed.