Two-Photon Ionization of Single Atoms Localized on the Bessel Beam Axis

In the article the effect of twisting of Bessel radiation on two-photon ionization of single atoms localized on the axis of the incident beam is studied. The matrix element of two-photon ionization of this type is obtained for arbitrary polarization and multipolarity of the incident radiation. The differential and integral probability of ionization of an atom over the photoemission angle is analyzed. Illustrative calculations are performed for helium and neon atoms in the simplest case of a circularly polarized field in the electric dipole approximation in the single-active-electron model.