Relativistic fine structure oscillator strengths for Li-like ions: C IV - Si XII, S XIV, Ar XVI, Ca XVIII, Ti XX, Cr XXII, and Ni XXVI

Abstract

Abstract. Ab initio calculations including relativistic effects in the Breit-Pauli R-matrix (BPRM) method are reported for fine structure energy levels and oscillator strengths upto n = 10 and 0 ≤ l ≤ 9 for 15 Li-like ions: C IV, N V, O VI, F VII, Ne VIII, Na IX, Mg X, Al XI, Si XII, S XIV, Ar XVI, Ca XIII, Ti XX, Cr XXII, and Ni XXVI. About one hundred bound fine structure energy levels of total angular momenta, 1/2 ≤ J ≤ 17/2 of even and odd parities, total orbital angular momentum, 0 ≤ L ≤ 9 and spin multiplicity (2S + 1) = 2, 4 are obtained for each ion. The levels provide almost 900 allowed bound-bound transitions. The BPRM method enables consideration of large set of transitions with uniform accuracy compared to the best available theoretical methods. The CC eigenfunction expansion for each ion includes the lowest 17 fine structure energy levels of the core configurations 1s 2 , 1s2s, 1s2p, 1s3s, 1s3p, and 1s3d. The calculated energies of the ions agree with the measured values to within 1% for most levels. The transition probabilities show good agreement with the best available calculated values. The results provide the largest sets of energy levels and transition rates for the ions and are expected to be useful in the analysis of X-ray and EUV spectra from astrophysical sources.

Energy levels, radiative rates and electron impact excitation rates for transitions in Be-like Ti XIX

“…Nevertheless, energy differences among these levels are very small. Finally, the BPRM energies of Nahar [14] have the same orderings as NIST and our calculations from GRASP. The BPRM energies also generally agree in magnitude, except for 4s,5s 2 S 1/2 levels for which they are lower by up to 0.2 Ryd, depending on the ion.…”

“…Included in these tables are our level energies from GRASP, obtained without and with the inclusion of Breit and QED effects, plus the experimental energies compiled by NIST. Also included in these tables are the theoretical energies obtained from our parallel calculations from FAC and those by Nahar [14] from the Breit-Pauli R-matrix (BPRM) code of Berrington et al [19]. The inclusion of the Breit and QED corrections decreases the level energies (except for level 2, i.e.…”

“…), in length form only, for all 92 electric dipole (E1) transitions among the 24 levels of Li-like ions with 12 ≤ Z ≤ 20. The indices used to represent the lower and upper levels of a transition have already been defined in Tables 1 (a-h In Tables A-H we compare our A-values from the GRASP and FAC codes for some of the common E1 transitions with those of Nahar [14] from the BPRM code of Berrington et al [19]. Also included in these tables are the f-values from our GRASP calculations.…”

“…Experimentally, energy levels for Li-like ions have been compiled by NIST (National Institute of Standards and Technology) and are available at their website http://www.nist.gov/pml/data/asd.cfm. Theoretically, energy levels and A-values have been calculated by Nahar [14] for transitions of 15 Li-like ions in the 6 ≤ Z ≤ 28 range. However, collisional atomic data are limited to transitions among the lowest three levels of Li-like ions with 8 ≤ Z ≤ 92, and from these levels to the higher excited levels of the n ≤ 5 configurations [15].…”

Plasma-screening effects in the astrophysically relevant He-like and Li-like Mg and Fe ions*

“…The X-ray spectra from these ions are observed from a large variety of astrophysical sources [1][2][3] and laser plasma interactions [4,5]. They are used to determine the primordial abundances of elements that are of immense interest for testing the big bang cosmology [6].…”