Beryllium-like Ions Research Articles

Relativistic Intermediate-coupling Calculations for Ions of the Beryllium Isoelectronic Sequence

Relativistic intermediate-coupling wavefunctions are used to evaluate wavelengths and oscillator strengths for the resonance transition 2S2 'SO -+ 2s2p 'P~ and the intercombination transition 2S2 'SO -+ 2s2p 3p~ for iron, krypton, molybdenum and tungsten beryllium-like ions. The convergence of the results with respect to the basis set of orbitals is considered. It is shown that the same degree of accuracy can be achieved by using the three configuration basis composed of 2S2, 2s2p and 2p2. The question of at what stage the Breit interactions should be included in the Hamiltonian is discussed. We also compare our calculated 2S2 'SO -+ 2s2p 3p~ intercombination oscillator strengths with those deduced from beam-foil experiments for iron and krypton

Spin-forbidden transitions between 2p 2 and 2s2p states in the beryllium isoelectronic sequence

Fine-structure splittings, wavelengths and transition probabilities are evaluated for transitions 2p21S0→2s2p3P10, 2p21D2→2s2p3PJ0 (J=1, 2) and 2p23PJ→2s2p1P10 (J =0, 1, 2) in beryllium-like ions using configuration interaction wavefunctions. Some significant differences with previous calculations are obtained. At present there are no experimental results. However, from calculations reported here it should clearly be worthwhile to search for these lines in laboratory and astrophysical spectra. The decay of the 2p21D2 level is discussed.

Electron-impact-ionization cross sections and rates for highly ionized berylliumlike ions

Electron-impact-ionization cross sections and rates for highly ionized berylliumlike ions

Ionisation cross sections with the inclusion of excitation-autoionisation contributions for ions with five or fewer bound electrons

Total ionisation cross sections with the inner-shell excitation autoionisation contribution included are obtained for lithium-like and beryllium-like ions in the ground and first excited levels and for boron-like ions in the ground level from scaled Coulomb-Born exchange results for hydrogenic ions. The effect of radiative decay of the autoionising levels is included using an approximate method suggested by Hahn (1978). The method of calculation is expected to be valid for Z/N>or approximately=2, where N is the number of bound electrons per ion. Fair agreement with the experiments of Crandall et al. (1979) is obtained for O4+ and C3+, where Z/N=2, and rather good agreement has been obtained for N4+ and O5+, where Z/N>2. For N 3 and appears to be insignificant for N>or approximately=5.

Intermediate coupling collision strengths for delta N = 0 transitions produced by electron impact on highly charged ions. II - Transitions between states of the 1/2s/2/2s/ and 1/2s/2/2p/ configurations and those of the 1/2s/2s2p configuration in beryllium-like ions

view Abstract Citations (17) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Intermediate coupling collision strengths for delta N = 0 transitions produced by electron impact on highly charged ions. II - Transitions between states of the 1/2s/2/2s/ and 1/2s/2/2p/ configurations and those of the 1/2s/2s2p configuration in beryllium-like ions Sampson, D. H. ; Clark, R. E. H. ; Golden, L. B. Abstract The theory given in the preceding paper is used to calculate the collision strengths and line strengths for all fine-structure transitions between states of the 1s22s2 and 1s22p2 configurations and those of the 1s22s2p configuration in beryllium-like ions with nuclear charge number Z in the range 14 ≤ Z ≤ 74. The results are found to be in mostly very good agreement with the data available by other means. They are expected to be useful in applications to high temperature plasmas such as occur in the coronal regions of the Sun and in controlled nuclear fusion research. Publication: The Astrophysical Journal Supplement Series Pub Date: October 1980 DOI: 10.1086/190690 Bibcode: 1980ApJS...44..193S Keywords: Beryllium; Electron Impact; Electron Transitions; Fine Structure; Ionic Collisions; Transition Probabilities; Atomic Energy Levels; Controlled Fusion; High Temperature Plasmas; Plasma Diagnostics; Solar Corona; Plasma Physics full text sources ADS |

Intermediate coupling collision strengths for delta N = 0 transitions produced by electron impact on highly charged ions. III - Transitions within the 1/2s/2s2p and 1/2s/2/2p/ configurations and between the 1/2s/2/2s/ and 1/2s/2/2p/ configurations in beryllium-like ions

Intermediate coupling collision strengths are obtained for all fine-structure transitions within the 1s/sup 2/2s2p and 1s/sup 2/2p/sup 2/ configurations and between the 1s/sup 2/2s2 and 1s/sup 2/2p/sup 2/ configurations in highly charged beryllium-like ions with Z in the range 14< or =Z< or =74. The results are expected to be useful in the study of high temperature plasma such as occur in the solar coronal regions and in fusion research.

Universal systematic sequence of even-tempered Gaussian primitive functions in electronic correlation studies

The possibility of developing a universal systematic sequence of eventempered Gaussian primitive functions for atomic and molecular electronic structure studies is examined. The radial beryllium-like ions are used to demonstrate this approach both within the Hartree-Fock model and by including correlation effects. Correlation energies are computed using the diagrammatic many-body perturbation theory. The Hartree extrapolation procedure is used to obtain empirical upper bounds to the basis set limit and the procedure of Schmidt and Ruedenberg is employed to obtain empirical lower bounds for the basis set limit. The convergence properties of the calculations with respect to the size of the basis set are examined.

Two-channel relativistic random-phase approximation applied to the photoionisation of helium- and beryllium-like ions

Atomic photoionisation cross sections including both relativistic and correlation effects for the helium and beryllium isoelectronic sequences are calculated in two-channel relativistic random-phase approximation (RRPA). By studying the relativistic E1 transition along the sequence, the coupling between the low-energy photoelectron and the core electron (electrons) is found to deviate from relativistic jj coupling even for high Z elements. The deviation of the sum of dipole oscillator strength from the non-relativistic Thomas-Reiche-Kuhn rule is also investigated.

The 2s2p(3P10)→2s2(1S0e) intercombination in beryllium-like Mg IX, Si XI, Ar XV, Ca XVII and Fe XXIII

Transition probabilities are evaluated for the 2s2p(3P10) to 2s2(1S0e) transition in beryllium-like ions for Mg IX, Si XI, Ar XV, Ca XVII and Fe XXIII using configuration interaction wavefunctions.

Breit-Pauli approximation for highly ionised beryllium-like ions up to Fe XXIII

The authors have calculated oscillation strengths and transition probabilities for transitions between the 1s22s2, 1s22s2p and 1s22p2 states, namely: 1S0e to 1P10; 1P10 to 1D2e; 1P10 to 1S0e and 3PJ0 to 3PJ'e. For allowed transitions, use of elaborate wave-functions is more important than relativistic corrections up to Z approximately=14. For higher Z, relativistic corrections become somewhat more important.

The use of Breit interaction: the3P1to1S0intercombination line in beryllium-like systems

Transition probabilities are evaluated for the 2s2p 3P1 to 2s2 1S0 transition in beryllium-like ions for Z=4-10 and Z=14, using configuration-interaction wavefunctions. The convergence of the results with respect to the basic set of orbitals is considered. The question of at what stage the Breit interaction should be included in the Hamiltonian is discussed.

Excitation of Beryllium-Like Ions by Electron Impact

The Coulomb-Born approximation has been used to calculate the cross sections of electron impact excitation in beryllium-like ions (C III, N IV, O V and Ne VII) for the 2s 2 1 S→2s2p 1 P transition. In order to be applicable to high-temperature plasmas the cross sections for respective ions have been obtained at impact electron energies from threshold to 4 keV.

Electron-impact excitation of highly charged berylliumlike ions with inclusion of configuration mixing

Electron-impact scaled collisions strengths ${Z}^{2}\ensuremath{\Omega}$ for a large number of transitions involving configuration-mixed initial and/or final states are obtained for berylliumlike ions in the limit $Z\ensuremath{\rightarrow}\ensuremath{\infty}$. These results are compared with the corresponding non-configuration-mixed results. It is found that the effect of configuration mixing is usually small (\ensuremath{\lesssim}30%) and nearly independent of impact electron energy, but in a very few cases it is large, resulting in a change in $\ensuremath{\Omega}$ by about a factor of 2. The results are expected to be of interest for applications to high-temperature plasmas containing moderately heavy elements.

Radiation losses in a dense high-temperature hydrogen plasma containing impurities

The authors calculate the radiation intensity of a hydrogen plasma containing small amounts of impurity in the form of bare nuclei and hydrogen-, helium-, lithium- and beryllium-like ions with a nuclear charge Z in the range 5 ≤ Z ≤ 18. They consider electron concentrations of 1016 ≤ ne ≤ 1020 cm−3 and electron temperatures of 0.05 ⩽ kT/Z2 Ry ⩽ 3 (Ry = 13.6eV), which are typical of the radiating zone of the plasma focus. The results show, among other things, that the radiation from the impurities may substantially limit the life-time of the high-temperature zone in the plasma focus.

Measurements of Collisional-Excitation Rate Coefficients for Berylliumlike Ions

Electron collision-excitation rate coefficients have been determined experimentally for excited singlet and triplet ($(n=2,3, \mathrm{and} 4$) levels of the berylliumlike ions N IV, O V, Ne VII, and Si IX using various plasma cases produced in a $\ensuremath{\theta}$-pinch device. Line intensities of these ions were measured absolutely and converted into rate coefficients by knowledge of the pertinent plasma parameters. Electron density and temperature were obtained as function of radius and time from the spectrum of scattered laser light. The intercombination transition $2s2p^{3}P\ensuremath{\rightarrow}2{s}^{2}^{1}S$ was observed, and its absolute intensity allowed determining the metastable triplet level population. The probable error of any individual rate coefficient is estimated to be a factor of 2.

Collisional Ionization Rates for Lithium- and Beryllium-Like Ions

Collisional ionization rates for C IV, N V, and O VI as well as for O V and Ne VII are deduced from the time history of spectral lines emitted by these ions in a hot plasma. The plasma (in the electron temperature range 100-260 eV) is produced in a 15-kJ theta-pinch device, and it is analyzed using the light-scattering technique. The results are consistent with theoretical calculations for O VI and with a semiempirical formula based on theoretical calculations for hydrogenic ions but smaller by factors 1.5-2.

The extended Hartree-Fock equations for atoms

The consequences of adopting a precise definition of the extended Hartree-Fock scheme proposed in an earlier paper are examined. It is shown that the extended Hartree-Fock scheme can correct for the zero-order mixing of configurations for certain, but not all, states of small atoms. An earlier calculation of the second-order extended Hartree-Fock energy of the ground states of beryllium-like ions is shown to be in error and the correct value is calculated by an alternative but more accurate and yet simpler method. The extended Hartree-Fock scheme is shown to give an augmented significance to the perturbation treatment of Hartree-Fock equations. It is also shown that in this scheme the purely variationally determined mixing coefficients for configurations depend, in general, on the nuclear charge Z.