Comprehensive calculations of energy levels, radiative transition parameters, hyperfine structure constants A_J - B_J, Landé g_J factors and isotope shifts for Sc XX

Atomic parameters are crucial for calculating stellar opacities, chemical abundance, developing sophisticated stellar atmosphere models, plasma diagnosis and modelling. Isotope shifts (IS) and hyperfine structures (HFS) are essential for precise and correct spectra analysis. Recently, studies on scandium have become an exquisite research topic as its energy levels, transition rates, weighted oscillator strengths, HFS are needed for the accurate study of nucleosynthesis processes, abundance anomalies in stars and plasma diagnosis. Sc is usually present in its ionic form in high-temperature plasma, and He-like ions have dominant features in X-ray spectra of stars. Therefore we carry out large scale calculations of the energy levels, transition rates for multipole transitions, lifetimes, HFS constants, Landé g_J factors, and IS factors for the lowest 127 levels of Sc XX using the multi-configurational Dirac–Fock procedure. GRASP2018 and RIS4 packages are used to perform the computation. The leading quantum electrodynamic corrections, Breit interaction, nuclear recoil effects and electron correlation effects on the atomic structures are also studied. An excellent agreement with the previously available results is observed. A large section of the results is reported for the first time.