Theoretical study of transitions involving three rydberg series in two‐valence electron systems: MgI and its electronic sequence

Z Phys D - Atoms, Molecules and Clusters

Barrientos

1994

Abstract. Oscillator strengths tor 2sns IS~2smp ~pO transitions of several ions in the beryllium isoelectronic sequence (BeI-CrXXI) have been computed and analyzed. The quantum defect orbital method, including core-polarization effects through an effective dipole-moment transition operator, has been followed. Comparisons are made between various theoretical and experimental data and those predicted here. It is shown that the quantum defect orbital formalism adequately describes transitions in these atomic systems.

“…[10,11,14,15]), are obtained through the analytical solution of the one-electron Schr6dinger equation containing an effective central field potential of the form,…”

Section: Methodsmentioning

confidence: 99%

“…The calculations have been made with explicit inclusion of the effects of the interaction of the polarized core with the outer electrons, as was earlier done in the magnesium isoelectronic sequence also with two valence electrons [14]. No significant differences have been found between the calculated RQDO and QDO f-values.…”

Section: Introductionmentioning

confidence: 99%

Isoelectronic smoothing of energy levels and calculations on the 2sns 1 S→2smp 1 P 0 transitions in the beryllium isoelectronic sequence

Virumbrales

Z Phys D - Atoms, Molecules and Clusters

Barrientos

1994

“…It is difficult to derive a general expression for f (r). In previous work (Martin et al 1990) we have used the expression proposed by Caves and Dalgarno (1972):…”

Section: Quantum Defect Orbital (Qdo) Calculationsmentioning

confidence: 99%

Relative and absolute dipole oscillator strengths in the Rydberg series of Cd I

Ahmad

Griesmann

J. Phys. B: At. Mol. Opt. Phys.

et al. 1996

Relative dipole oscillator strengths for the transitions 5s 2 1 S 0 → 5snp 1 P 1 (8 n 13) in cadmium have been measured using magneto-optical rotation spectroscopy in the VUV. The uncertainty in the relative oscillator strengths is estimated to be 3%. Absolute oscillator strengths were determined on the basis of the known oscillator strength of the 5s → 11p transition. Our experimental results agree with quantum defect orbital calculations which we have carried out for transitions in the principal series in cadmium up to 5s → 32p. A revised value of 4 ± 2 Mb for the total photoionization cross section at the ionization threshold is proposed.

“…Core polarization effects are implicitly included in the calculations as they are accounted for in the Λ parameter of the model Hamiltonian, as it contains the experimentally determined quantum defect. In some of our previous papers (see e.g., Martín et al 1989) we have, additionally, introduced a core-polarization correction term in the transition operator. However, it is our experience that moderately -to highly-ionized atoms are rather insensitive to the explicit introduction of a core-polariation correction in the transition moment.…”

Section: Relativistic Quantum Defect Orbital Calculationsmentioning

confidence: 99%

MCDF and RQDO study of the fine-structure lines of transition arraynp$^2 \to n$p $(n+1)$s in isoelectronic atomic systems

Charro

2002

A&A

Abstract. Relativistic calculations of electric dipole (E1) allowed transition for a number of ions in the germanium sequence have been performed. Oscillator strengths for fine-structure transitions within the 4p 2 -4p5s array have been calculated with both the Multiconfigurational Dirac-Fock (MCDF) approach and the Relativistic Quantum Defect Orbital (RQDO) method. The results are analysed on the grounds of the theoretical data available in the literature. Also, a comparative analysis with the homologous silicon sequence is made. The spectra of systems such as Mo XI are important in the context of plasma physics and thermonuclear fusion measurements.Key words. atomic data -line: identification IntroductionThe detection of heavy trace elements with nuclear charge numbers Z ≥ 30 in the planetary nebula (PN) NGC 7027 (Péquignot & Baluteau 1994) has opened up interesting scientific possibilities in astrophysics. Ge I has been observed in the spectra of Ap and Bp stars (Adelman et al. 1979) and in the solar photosphere (Moore et al. 1966), and the determination of the chemical composition of the stars depends in a sensitive way on the availability of accurate transition probabilities. The study of elemental abundances of heavy elements (Z ≥ 30) in the interstellar medium allows the exploration of the possible effects of local chemical enrichment and mixing in the interstellar gas and also the nature of the condensation of elements from the gas phase on dust (Savage 1993;Cardelli 1994;Morton 1996). These heavy elements have derived from nuclear processes (slow and rapid neutron captures on to light elements generated by different stellar progenitors) that differ from those producing Zn and the lighter elements (element burning occurring at high temperature, Cameron 1982).Most atoms and ions in the interestellar medium are observed in their ground energy states because of their low collisional excitation rates, and their resonance lines appear generally in the UV region. The high-resolution gratings of the Goddard High Resolution Spectrograph aboard the Hubble Space Telescope now allow the detection of very weak absorption lines. As a consequence, it becomes possible to investigate absorption lines of some heavy elements, the cosmic abundances of which are rather low (several times smaller than that of hydrogen by number) (Biémont et al. 1998).Send offprint requests to: E. Charro, e-mail: lmnieto@wamba.cpd.uva.es Experimentally, the spectra of some Ge-like ions have been analysed. Several transition arrays have been studied for the ions Y VIII -Mo XI (Rahimullah et al. 1976(Rahimullah et al. , 1978Chaghtai et al. 1980;Ateqad et al. 1984) on the basis of spectrograms obtained at Lund University. The 4p-5s transition of Ru XIII, Rh XIV and Pd XV has been observed in laser-produced plasmas by O'Sullivan et al. (1988). Emission spectra of Rb VI (O'Sullivan & Maher 1989) and Sr VII (O'Sullivan 1989) produced by the same technique have been photographed in the 40-500 and 250-500 Å regions, respectively, leading to the ident...