Nondipole effects in the photoionization of neon: Random-phase approximation

The random-phase approximation (RPA) is applied to study nondipole corrections to the angular distribution of photoelectrons from the $n=2\mathrm{}$ shell of Ne. Calculations of the parameters ${\gamma }_{\mathrm{nl}}$ and ${\delta }_{\mathrm{nl}}$ arising from $E_1-E_2$ interference effects are carried out for the $2s$ and $2p$ subshells of Ne in the photon energy range 100–2000 eV. For the $2s$ shell, the RPA calculations show small effects of correlation near the $2s$ threshold energy, but are otherwise in agreement with independent-particle approximation (IPA) calculations. The RPA and IPA values of ${\gamma }_{2s}$ are also in agreement with experiment. For the $2p$ shell, a small difference between RPA and IPA calculations of the nondipole parameters is found for energies near the $1s$ threshold; however, both RPA and IPA calculations of the parameter ${\gamma }_{2p}+3\mathrm{}{\delta }_{2p}$ disagree significantly with experimental measurements for photon energies above 1000 eV.