# ICHEP 2020

28 July 2020 to 6 August 2020
virtual conference
Europe/Prague timezone

## Many Body Perturbation Theory of energy levels, wavelengths, oscillator strengths, radiative rates and lifetimes of He-like Lithium

31 Jul 2020, 13:35
3m
virtual conference

#### virtual conference

Poster 14. Computing and Data Handling

### Speaker

Ms Soumaya Manai (National Centre for Nuclear Sciences and Technologies (CNSTN), Tunisia)

### Description

In recent years, there have been extensive spectroscopic studies, both experimental and theoretical, of helium isoelectronic sequence. Such an analysis requires information for a wide range of atomic parameters, including energy levels, wavelengths, oscillator strengths, radiative rates and lifetimes. Our aim was to provide a set of accurate energy levels, wavelengths, oscillator strengths, radiative rates and lifetimes for helium-like ions. Accurate energy levels calculations among the lowest 71 levels arising of $1s^{2}$ and $1snl$ ($n\leq6$, $l\leq(n-1)$) configurations of He-like lithium are carried out through the standard relativistic configuration interaction $(RCI)$ approach, the second-order many body perturbation theory $(MBPT)$ [1]. The calculation methods are derived by a modified self-consistent Dirac-Fock-Slater iteration. We have also considered relativistic effects by incorporating quantum electrodynamics (QED) and Breit corrections. We provide accurate calculations of energy levels, wavelengths, radiative rates and lifetimes of all types of transitions ($E1$, $E2$, $M1$ and $M2$) for He-like lithium. The use of the $MBPT$ approach significantly improves the value of the energy levels. The maximum difference relative to the NIST data [2] becomes $651\: cm^{-1}$ while the majority of values of energy levels of $RCI$ method are decreased by approximately $5000 \:cm^{-1}$. The average relative deviation don't exceed $5\%$ for the three methods compared to the results from NIST. For the MBPT calculations we have $-0.47\pm 0.90\%$, for the RCI calculations we have $2.62\pm 1.70\%$ and for the standard FAC calculations we have $3.13\pm 1.60\%$. The present results are in good agreement with already published data in the literature (theoretical [3] and experimental data). Several new energy levels were found out where no other theoretical or experimental results are available. We expect that our extensive calculations will be useful to experimentalists for identifying the fine-structure levels [4].
[1] MF. Gu, Canadian Journal of Physics, 86, 675–689, (2008).
[2] Kramida, A., Ralchenko, Yu., Reader, J., and NIST ASD Team (2018). NIST Atomic Spectra Database (ver.
5.5.2), [Online]. Available: https://physics.nist.gov/asd [2018, February 20]. National Institute of Standards and Technology, Gaithersburg, MD.
[3] KM. Aggarwal, T. Kato, FP. Keenan, I. Murakami, Physica Scripta J, 83, 015302, (2010).
[4] A.M. Cantu, W.H. Parkinson, G. Tondello and G.P. Tozzi, Opt. Soc. Am J. 67, 1030-1033, (1977).

### Primary authors

Ms Soumaya Manai (National Centre for Nuclear Sciences and Technologies (CNSTN), Tunisia) Dr Dhia Elhak Salhi (National Centre for Nuclear Sciences and Technologies (CNSTN),Tunisia)

### Co-author

Prof. Haikel Jelassi (National Centre for Nuclear Sciences and Technologies (CNSTN), Tunisia)

### Presentation Materials

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