Nondipolar photoionization of atoms

Abstract. Results of the nondipolar angular distribution parameter γ are presented for two cases of photoionization with substantially different photon energies, Kr 1s in the hard x-ray regime, and He 1s in the vuv regime. The nondipolar asymmetries are apparent even at low energies. The presence of dipole and quadrupole resonances strongly modifies the energy dependence of the nondipolar asymmetry parameter γ. Measurements of γ can be used as a spectroscopic tool to characterize quadrupole resonances that are not accessible in photoabsorption measurements