Ni XIX Research Articles

Implementation and application of the relativistic equation-of-motion coupled-cluster method for the excited states of closed-shell atomic systems

We report the implementation of equation-of-motion coupled-cluster (EOMCC) method in the four-component relativistic framework with the spherical atomic potential to generate the excited states from a closed-shell atomic configuration. This theoretical development will be very useful to carry out high precision calculations of varieties of atomic properties in many atomic systems. We employ this method to calculate excitation energies of many low-lying states in a few Ne-like highly charged ions, such as Cr XV, Fe XVII, Co XVIII and Ni XIX ions, and compare them against their corresponding experimental values to demonstrate the accomplishment of the EOMCC implementation. The considered ions are apt to substantiate accurate inclusion of the relativistic effects in the evaluation of the atomic properties and are also interesting for the astrophysical studies. Investigation of the temporal variation of the fine structure constant (\alpha) from the astrophysical observations is one of the modern research problems for which we also estimate the \alpha sensitivity coefficients in the above ions.

Energy Levels, Oscillator Strengths, and Transition Probabilities of Ni XIX and Cu XX

Energy levels, oscillator strengths, and transition probabilities, for the 1s2 2s2 2p6, 2p53l (l = 0, 1, 2), 2p54l (l = 0, 1, 2, 3) states in Ni XIX and Cu XX are calculated using COWAN code. The Correlation and relativistic effects are considered. The calculations are compared with other results in the literature. A good agreement is found. We also report on some unpublished energy values.

Effective collision strengths for transitions in Ni XIX

Aims. In this paper we report electron impact collision strengths and excitation rates for transitions among the lowest 89 levels of Ni xix. Methods. The Dirac atomic R -matrix code (darc) is adopted for the calculations of collision strengths and subsequently the effective collision strengths. Results. Collision strengths for resonance transitions among 89 levels arising from the (1s 2 ) 2s 2 2p 6 , 2s 2 2p 5 3$\ell$, 2s2p 6 3$\ell$, 2s 2 2p 5 4$\ell$, and 2s2p 6 4$\ell$ configurations of Ni xix are reported over a wide energy range below 250 Ryd. Additionally, effective collision strengths for all 3916 transitions among the 89 levels are listed over a wide temperature range below 10 7 K. Comparisons are made among different calculations and the accuracy of the data is assessed. Finally, comparisons between theoretical and experimental intensity ratios of some prominent lines of Ni xix are discussed.

Photoionization Cross Section for Ni xix

The relativistic R-matrix method is used to calculate photoionization cross section for the ground state 1s22s22p6 1Se (J = 0) and the first four excited states (J = 0 even) of Ne-like Ni XIX, using the lowest 68 target states of Ni XX. Cross sections are dominated by Rydberg series of autoionizing resonances converging to several ionic states. We have compared our new 68-level cross sections with 32-level and with much lower 3-levels calculations. The 3-level results are found to be inadequate for practical applications due to the lack of complete set of resonances converging at higher thresholds. In our calculations, we have taken all the important physical effects like exchange, channel coupling, and short-range correlation, as well as relativistic effects into account. Our present results can be useful for modeling ionization balance of Ni XIX in laboratory and astrophysical plasmas. We believe that this is the first relativistic calculation for this ion to obtain the photoionization cross section.

Collision strengths for transitions in Ni XIX

In this paper we present calculations of electron impact excitation collision strengths for transitions among the 89 fine-structure levels of the 2s22p6, 2s22p53l, 2s2p63l, 2s22p54l, and 2s2p64l configurations of Ni XIX, for which flexible atomic code (FAC) has been adopted. Comparisons are made with the earlier available results in the literature, and the anomalies observed have been discussed.

Electron impact excitation of Ne-like Ni XIX

In this paper we report atomic data, namely energy levels, radiative rates, lifetimes, collision strengths, and excitation rate coefficients, for transitions among 89 levels of the (1s2) 2s2 2p6, 2s2 2p53l, 2s2p6 3l, 2s2 2p54l, and 2s2p64l configurations of Ni XIX. For the calculations of energy levels and radiative rates the grasp code has been adopted, whereas for the calculations of collision strengths darc is employed.

The3C/3DLine Ratio in Ni XIX: NewAb InitioTheory and Experimental Results

We report a fully relativistic close-coupling calculation of the electron impact excitation of Ni xix to derive the 3C/3D line intensity ratio, with an uncertainty of 5%. Convergence of the calculation with respect to both channel coupling effects and the many interacting Rydberg series of resonances has been achieved. New measurements in an electron beam ion trap agree with our calculation. We show that the 3C/3D x-ray line ratio depends sensitively on both electron energy and beamwidth in an optically thin plasma. Accounting for this dependence improves the accuracy of the Ni abundance determination in astrophysical sources.

Energy levels and radiative rates for transitions in Ni XIX

Aims. In this paper we report calculations for energy levels and radiative rates for transitions in Ni XIX. Methods. The General purpose Relativistic Atomic Structure Package (GRASP) has been adopted for the calculation of energy levels and radiative rates. Results. Energies for the lowest 89 levels from the (1s 2 ) 2s 2 2p 6 , 2s 2 2p 5 3l, 2s2p 6 3l, 2s 2 2p 5 4l and 2s2p 6 4l configurations of Ni XIX, are reported. Additionally. radiative rates, oscillator strengths, and line strengths are reported for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among these levels. Comparisons are made with the available results in the literature, and the accuracy of the present data is assessed. Finally, lifetimes for all excited levels are listed, and comparisons made with earlier available theoretical results.

Electron impact excitation collision strengths for neon-like Ni XIX calculated using the relativistic R-matrix method

In a recent paper [Pramana — J. Phys. 64, 129 (2005)] results have been presented for electron impact excitation collision strengths for transitions among the fine-structure levels of the 2s22p6 and 2s22p53s configurations of Ni XIX. In this paper we demonstrate through an independent calculation with the relativistic R-matrix code that those results are unreliable and the conclusions drawn are invalid.

Collisional excitation of neon-like Ni XIX using the Breit-PauliR-matrix method

Collision strength for the transition within the first five fine-structure levels in Ni XIX are calculated using the Breit-PauliR-matrix method. Configuration interaction wave functions are used to represent the target states included in theR-matrix expansion. The relativistic effects are incorporated in the Breit-Pauli approximation by including the one-body mass correction, Darwin and spin-orbit interaction terms in scattering equations.

Laboratory Measurements of 3 → 2 X-Ray Emission Lines of Ne-like Ni xix

The intensity ratios between 3 → 2 emission lines in Ni XIX were measured on the Livermore electron beam ion trap (EBIT-I) with a flat-field grating spectrometer and the NASA/Goddard Space Flight Center X-ray microcalo-rimeter. The results are consistent with earlier measurements of Fe XVII and other Ne-like ions at Livermore and confirm the problems in the atomic modeling of the direct collisional excitation for Ne-like systems.

Photoionisation of Ground State of Ni XIX Using a Relativistic Breit–Pauli Approximation

The relativistic Breit–Pauli approximation is used within the R-matrix method to calculate photoionization cross-sections from the ground state of Ni XIX. Relativistic effects are clearly revealed by comparing the results with those obtained in the non-relativistic LS coupling approximation.

The observation of the Ne-like ion resonance line satellites for Cr XV ··· Ni XIX CO2-laser produced plasma

We present an analysis of dielectronic satellite spectra of Ne-like ion resonance lines for elements from Cr to Ni. For these low-Z elements, we use spectra from strongly underionized CO2-laser produced plasma to minimize the emission from open L-shell ions. This simplifies the spectra and allows the identification of satellite lines caused by radiative transitions from autoionizing states of sodium like ions. Good agreement between the satellite structure calculations and the experimental emission spectra is obtained.

Electron impact excitation of Ni XIX using theR-matrix method

Collision strengths for all the transitions between the 15 lowest states of neon-like Ni XIX have been calculated for electron impact in the 80–140 Ry energy range. Configuration-interaction wavefunctions have been used to represent the target states. The standardR-matrix code has been used to calculate the lower scattering partial waves (L≤9), while a no-exchange version of the same code has been used to compute efficiently the higher partial waves (L≥10). Effective collision strengths for 105 excitation transitions between the ground state 2s22p61Se and the 142s22p53l Rydberg states are tabulated for electron temperatures in the range logT=5.40 to logT=7.00, withT expressed in °K.

Allowed and forbidden transitions in highly ionized neon-like atoms (Ni XIX-U LXXXIII)

Energy levels are calculated for highly ionized atoms of the neon sequence (Ni XIX to U LXXXIII). The multiconfigurational Dirac-Fock (MCDF) method, combined with semi-empirical corrections to the ab initio values of the energy levels, has been used for the calculations. Oscillator strengths are tabulated for 2p-3s, 2p-3d, 3s-3p and 3p-3d electric dipole (E1) transitions and for some Δn = 1 forbidden (E2, M1 and M2) lines originating from the ground state.

A beam-foil study of Ni XIX and Cu XX and a theoretical survey of 2p53l configurations from Ar IX to Cu XX

The spectra of the neon-like ions Ni XIX and Cu XX have been studied by beam-foil techniques. About 30 lines have been used in each spectrum to derive the energy levels of the 2p53l configurations. The identifications are supported by systematic theoretical studies using the Slater-Condon parametric method with isoelectronic constraints in the fitting process, and the ab initio relativistic parametric potential method. Some earlier identifications have been revised in the sequence Ar IX-Cu XX.

On the 3s-3p and 3p-3d Transitions in Ne-like Ni XIX

An experimental and theoretical study has been made of the 3s-3p and 3p-3d transitions in Ni XIX. The method of beam-foil spectroscopy, using 30-64 MeV Ni ions from a tandem accelerator, has been combined with theoretical calculations using the multiconfiguration Dirac-Fock (MCDF) program.

2s22p53s-2s2p63s transitions in the Ne I-like ions of chromium, iron and nickel from TFR-tokamak-produced plasma

Lines belonging to the Ne I-like, CrXV, Fe XVII, Ni XIX, Delta n=0 transitions 2s22p53s-2s2p63s, emitted around 100 AA have been identified in the TFR tokamak plasma.

The 2p53s, 3p and 3d Configurations in Neon-Like Ti XIII and Fe XVII

Spectra emitted from laser-produced plasmas of scandium, titanium, vanadium and chromium have been recorded in the region 270-600 Å, and lines belonging to the 3s-3p and 3p-3d transition arrays in neonlike ions have been identified. The 2p53s, 3p and 3d energy levels have been derived from the observations for Ti XIII and from solar flare lines for Fe XVII. Hartree-Fock calculations and parametric fits have yielded scaling factors for ab initio energy integrals that make it possible to predicts 3s-3p and 3p-3d wavelengths. Observed and predicted wavelengths for the strongest lines in Sc XII, V XIV, Cr XV and Ni XIX are presented.

Identifications of Fe XVII and Ni XIX in solar flares based on isoelectronic extrapolations

On a identifie vingt-quatre raies dans le spectre d'une eruption solaire dans la region 200-410 A comme des transitions entre les configurations 2s 2 2p 5 3s, 3p et 3d dans Fe XVII et Ni XIX