Nondipole Effects in Photoionization of Rare Gas Atoms

We present a discussion of octupole and other O(k2) (k = 2π/λ, where λ is the photon wavelength) corrections to to the angular distribution of photoelectrons from noble-gas atoms. These corrections are characterized by four parameters ∆β, λ, μ, and ν constrained by λ+μ+ν = 0. As an example, we consider photoionization of n = 2 shell of neon for photon energies below 2 keV. The resulting angular distribution accounts for a significant part of the differences between experimental values of the non-dipole parameters for the n = 2 shell of neon and previous theoretical predictions.