R. V. Koneev | Searcharxiv

arXiv2026

Non-dipole effects in two-photon sweeping of the K-shell of an atomic ion

In the work [1], within the framework of a dipole approximation for the radiation transition operator, of the second-order nonrelativistic quantum perturbation theory and the Hartree-Fock single-configuration approximation, the first theoretical study of the generalized cross-section of the direct two-photon sweeping out of the K-shell of a light neon atom was carried out. In this Letter we supplement the Preprint [2] with the results of taking into account non-dipole effects when constructing the amplitude of the probability of the radiation transition between continuum-spectrum states. As the main result, it was found that the non-dipole effects reduce the generalized cross-sections of two-photon sweeping out of the K-shell of an atomic ion (Fe16+) the calculated in the dipole approximation by several orders of magnitude (giant non-dipole effect).

physics.atom-ph↗

arXiv2025

Two-photon sweeping out of the K-shell of a heavy atomic ion

Within the framework of the second-order non-relativistic quantum perturbation theory, the methods of the theory of irreducible tensor operators, and nonorthogonal orbitals, the absolute values and shape of the generalized cross-sections of the two-photon double ionization (sweeping) of the K-shell of a heavy neon-like ion of an iron atom were predicted. The complete wave functions of the ground state of the ion and the states of its ionization are obtained in the single-configuration Hartree-Fock approximation. The effects of radial relaxation of ionization states in the field of one and two vacancies in the K-shell are taken into account. The matrix element of the operator of the radiation transition between continuum-spectrum states is taken into account by introducing a correlation function. It was established that the generalized cross-section of the two-photon sweeping of the K-shell at high (greater than or equal to 15.8 keV) energies of absorbed X-ray photons is several orders of magnitude greater than the generalized cross-section of the two-photon single ionization of the K-shell. This result qualitatively reproduces the work of Novikov S.A. and Hopersky A.N. (J. Phys. B 2002. V. 35. P. L339), stimulates future research, in particular, the effects of cascade "evaporation" of electron shells of an atom (atomic ion) when filling an empty K-shell and can be tested in X-ray free-electron laser experiments with high peak radiation brightness and ultrashort photon pulse duration. The scheme of the proposed experiment with two linearly polarized X-ray photons is presented.

physics.atom-ph↗