Ibrahima Sakho

Title : Calculations of resonance energies of rydberg series of S4+ions in the framework of the modified atomic orbital theory

Abstract:

We intend to present the modified atomic orbital (MAOT) which is the second semi-empirical method of photoionization applied to the calculation of the resonance energies of Rydberg series of S⁴⁺ions. We will start with a brief description of the MAOT formalism. The opportunities to use the MAOT formalism for the study of the Photoionization of atomic species will be enlighten. The main ab initio methods of Photoionization based on the use of specific codes. To name a few, the widely used R-matrix approach is based on the Dirac Atomic R-matrix Code (DARC) whereas the MCDF method is based on the Code of Bruneau. Calculations of resonance energies of the Rydberg series of a given atomic system is very time consuming using the R-matrix or the multi-configuration Dirac–Fock (MCDF) formalism. In contrast with the ab inition methods, calculations of resonance energies is very easy when using the MAOT formalism. Direct calculations can be done from analytical formulas by only varying the principal quantum number of the optical electron. After, we will present the recent results on the calculation of the resonance energies and quantum defects of the Rydberg series 2s²2p⁵ 3s²nd (¹P₁, ³D₁), 2s²2p⁵ 3s² ns (¹P₁, ³D₁) and 2s2p⁶3s² np (¹P₁) Rydberg series of S⁴⁺ ions (Gning and Sakho, 2024. Iranian Journal of Science https://doi.org/10.1007/s40995-024-01599-8). Data are tabulated for 3 £ n £ 40. Comparison will be done with first synchrotron radiation measurements and theoretical calculations (MCDF and R-matrix) of Mosnier et al. Phys Rev A 106:033113. https://doi.org/10.1103/PhysRevA.106.033113.

Audience Take Away:

• Easy application of the MAOT to study the photoionisation of atomic system
• Help researchers on the field for the complete description of the atomic spectra investigated with the possibilities to extend experimental measurements to highly excited states.
• This is the main opportunity. Students can establish their own semi-empirical formula for a given atomic Rydberg series and proceed to the calculations of resonance parameters (resonance energies and widths)  using a simple scientific calculator of from an Excel program
• The work is devoted to the scientific community focusing their studies on the Photoionization  of atomic species for the diagnostic of astrophysical or laboratory plasmas.

Biography:

Prof Ibrahima Sakho study Physics and Chemistry at the University Cheikh Anta Diop, Dakar Senegal where he obtained his advanced degree in physical chemistry in 1997. He presented in his PhD thesis in atomic and nuclear physics in 2013 the first SCUNC semi-empirical method of photoionisation. He collaborated at SOLEIL in France where R-matrix, MCDF and SCUNC approaches were used successfully (Al Shorman et al. J. Phys. B 46, 195701 (2013); Gharaibeh et al. J. Phys. B: 47, 065201 (2014); McLaughlin et al. J. Phys. B 47, 115201 (2014); MNRAS 465, 4690–4702 (2017). He published more than 60 photoionization papers.