Extended analysis of six-times ionized barium (Ba VII)

Stellar laboratories

“…It was then extremely difficult to establish an unambiguous correspondence between the calculated values and the experimentally determined level energies. The use of radial parameters published by Sharma et al (2013) was unfortunately not of great help for making the identifications more reliable, the set of interacting configurations being not the same as the one considered in our work. For the levels considered in our fitting process, the mean deviations between calculated and experimental values were found to be equal to 140 cm −1 (even parity) and 196 cm −1 (odd parity).…”

“…To our knowledge, the only available data were recently published by Sharma et al (2014) and Sharma et al (2013) for Ba v and Ba vii, respectively. More precisely, these authors reported oscillator strengths and transition probabilities computed using rather limited configuration interaction models based on the Hartree-Fock approach due to Cowan (1981) combined with a semi-empirical least-squares fit of radial energy parameters.…”

“…More precisely, these authors reported oscillator strengths and transition probabilities computed using rather limited configuration interaction models based on the Hartree-Fock approach due to Cowan (1981) combined with a semi-empirical least-squares fit of radial energy parameters. In order to get a uniform set of oscillator strengths for all the transitions of Ba ions observed in the present work, we decided to perform new calculations including a larger amount of electron correlation and hence improving the previous investigations of Sharma et al (2013Sharma et al ( , 2014. The method adopted here was the relativistic Hartree-Fock (HFR) approach with core-polarization corrections (see e.g., Quinet et al 1999Quinet et al , 2002 2 5p6s6p, 5s5p 3 4f, 5s5p 3 5f, 5s5p 3 6f, and 5s5p 3 6p for the even parity.…”

“…Here also, we used the same core-polarization parameters as those considered for Ba v. The semi-empirical optimization process was carried out to adjust the radial parameters in 5s 2 5p 2 , 5p 4 , 5s 2 5p4f, 5s 2 5p6p, 5s5p 2 5d, 5s5p 3 , 5s 2 5p 2 5d, and 5s 2 5p 2 6s with the experimental energy Sharma et al (2013) below 350 000 cm −1 and 320 000 cm −1 for even and odd parities, respectively. In fact, it was found that many levels above those limits overlap unknown levels and are strongly mixed with states belonging to higher configurations such as 5s 2 4f 2 (even parity), 5s5p 2 4f, 5s 2 4f5d, and 5s 2 5p6d (odd parity).…”