Non-Dipole Angular Distributions and Helicity-Dependent Spin Polarization Near the Cooper Minimum of Na 3s

We report a theoretical investigation of non-dipole effects in the photoionization of the sodium 3s orbital by circularly polarized light, employing the relativistic multichannel formalism of Huang [1,2]. While the differential cross section remains identical for left- and right-circular polarization due to the target’s spherical symmetry the spin polarization of the photoelectrons exhibits a pronounced helicity dependence [3]. Our calculations explicitly include electric and quadrupole contributions, revealing significant deviations from the dipole approximation in both the angular distribution [4] and spin polarization in the vicinity of the Cooper minimum. Our results provide a complete relativistic description of spin–angle correlations for arbitrarily polarized photons and offer benchmark predictions for future spin-resolved experiments, with implications for the development of polarized electron sources and attosecond spectroscopy. [1] K.-M. Huand, Phys. Rev. A 22, 223 (1980); [2] K.-N. Huang. Phys. Rev. A 26, 3676 (1982); [3] S. Carlström, et al., Phys. Rev. Lett. 134, 093202 (2025); N. M. Hosea et al., Atoms 11, 125, (2023).