Sturmian basis set for the Dirac equation with finite nuclear size: Application to polarizability, Zeeman and hyperfine splitting, and vacuum polarization
Phys. Rev. A 112, 022816 – Published 21 August, 2025
DOI: https://doi.org/10.1103/tf1t-wj6w
Abstract
We investigate the application of the Sturmian basis set to relativistic atomic structure calculations. We propose a simple implementation of this approach and demonstrate its ability to provide various quantities for hydrogenlike ions, including binding energies, static dipole polarizability, the factor, hyperfine splitting, and nuclear magnetic shielding. Finally, we calculate the all-order (Wichmann-Kroll) vacuum-polarization charge density, which was a challenge for the finite-basis-set approach until recently. We present a comparison of the obtained results with previously published numerical and analytical calculations. All calculations are performed with nuclei of a finite size and can, in principle, be extended to arbitrary binding potentials.