Investigation of intravalence, core–valence and core–core electron correlation effects in polonium atomic structure calculations

Abstract

a b s t r a c tA detailed investigation of the atomic structure and radiative parameters involving the lowest states within the 6p 4 , 6p 3 6d, 6p 3 7s, 6p 3 7p and 6p 3 7d configurations of neutral polonium is reported in the present paper. Using different physical models based on the pseudo-relativistic Hartree-Fock approach, the influence of intravalence, core-valence and core-core electron correlation on the atomic parameters is discussed in detail. This work allowed us to fix the spectroscopic designation of some experimental level energy values and to provide for the first time a set of reliable oscillator strengths corresponding to 31 Po I spectral lines in the wavelength region from 175 to 987 nm.

Newly identified energy levels and calculated transition rates in astatine atom, the rarest element on Earth

“…This can be illustrated by the mean ratios of oscillator strengths obtained with two successive models for which the values were found to be equal to gf (B)/ gf (A) = 0.94 ± 0.08, gf (C)/ gf (B) = 1.00 ± 0.01, gf (D)/ gf (C) = 0.99 ± 0.03, gf (E)/ gf (D) = 1.00 ± 0.01 and gf (F)/ gf (E) = 0.99 ± 0.03 where the uncertainty represents the standard deviation. The same conclusions were already drawn when we considered the 6p 4 -6p 3 7s and 6p 3 7s -6p 3 7p transitions in the nearby atom of polonium [16] for which we highlihted on the other hand that the 6p 4 -6p 3 6d were more affected by the 6p 2 → 6d 2 double excitation and the 6s → 6d single excitation. This outcome was also verified in the case of 6p 5 -6p 4 6d transitions in At I but, in view of the total lack of experimental Table 3 Calculated oscillator strengths (log gf ) and transition probabilities ( gA ) for spectral lines connecting the experimentally known levels in 6p 5 a Air wavelengths deduced from the experimental energy levels [12] .…”

“…Predicted locations of the lowest odd-and even-parity configurations in astatine atom. [16] , francium ( Z = 87) [17] , radium ( Z = 88) [18] , actinium ( Z = 89) [18] and americium ( Z = 95) [19] .…”

Calculation of energy levels and electric dipole (E1) transition parameters for magnesium-like bismuth

“…We think that these cases occur due to some restrictions in two methods, and can be improved when configurations including more core-core correlations are considered, but program procedure doesn't run because of arising a huge number of levels. Similar studies which considered electron correlations for various materials have been reported recently [12][13]. As can be seen from the…”

Overview of recent advances performed in the study of atomic structures and radiative processes for the lowest ionization stages of heavy elements

“…To start to address this lack of data, and as a support to future experimental or theoretical studies, we performed atomic structure calculations on Po I using a theoretical approach including a large amount of electronic correlation and the most important relativistic effects [115]. More precisely, different models based on the HFR method were used for the first time for modelling the atomic structure and for computing radiative parameters involving the lowest states within the 6p 4 , 6p 3 6d, 6p 3 7s, 6p 3 7p, and 6p 3 7d configurations of neutral polonium.…”

“…2. Comparison of the calculated HFR wavelengths and weighted transition probabilities (gA) [115] with the experimental spectrum taken from the NIST compilation for the polonium atom (Po I) [117]. Pr IV [161] and Nd IV [162] ions.…”