Resonance enhancement of non-dipole effects in spin polarization of atomicphotoelectrons

Abstract

Resonances in quadrupole channels corresponding to thenp → εftransitions are investigated in atoms preceding Ce(Z = 59) andPa (Z = 91),where the 4f and 5f shells, respectively, start to be filled. These resonances lead toa prominent enhancement of all non-dipole effects in the angular distributionand spin polarization of photoelectrons at low photon energies of theorder of 100–200 eV. Since in atoms between Cd and Xe the 4p1/2photoline is absent from the photoelectron spectrum, we investigatethese effects in more detail in Hg where both 5p1/2 and5p3/2lines are present. We demonstrate that near these resonances the non-dipolecontribution to the degree of polarization of photoelectrons in Hg can be of theorder of 5%. For the absorption of linearly polarized light the degree ofpolarization due to the non-dipole contribution tends towards 100%, but thephotoelectron intensity in that case tends towards zero. Corrections to thephotoelectron intensities in the angular distributions at some angles can exceed10%. The similar resonance effects in Rn are expected to be substantiallystronger.