Semirelativistic description of Raman scattering of photons by hydrogenlike ions: comparison with relativistic and nonrelativistic approaches under the ionization threshold

Abstract Recently we constructed a semirelativistic and nondipole approach (SRNDA) for Raman scattering of light by hydrogenlike ions, by means of the discrete semirelativistic Coulomb Sturmian basis sets, the direct Foldy-Wouthuysen photon-atom interaction Hamiltonian and the expansion of photon fields in electric and magnetic multipoles [Meyap Soh C et al 2018 Ann. Phys. 395 196]. We also proposed its nonrelativistic version which involves the paramagnetic and diamagnetic terms of the semirelativistic Hamiltonian. Following these treatments, the purpose of this paper is twofold. First, we have completed that previous work with the derivation of the fully relativistic Raman scattering based on the well-known Dirac-Coulomb Sturmians of the first order. The formulas obtained, convenient for computer calculations, make it possible to accurately evaluate cross sections. Second, in an effort to reliably judge the credibility of the SRNDA and to assess its scope of applicability as far as the nuclear charge of atomic systems and the incident photons energy are concerned, we have carried out for concreteness computations of these schemes under the ionization threshold. They allow us to compare the various numerical predictions available, including those existing in the literature.