title: Electric-octupole and pure-electric-quadrupole effects in soft-X-Ray photoemission
abstract: Second-order [ O(k(2)), k = omega/c] nondipole effects in soft-x-ray photoemission are demonstrated via an experimental and a theoretical study of angular distributions of neon valence photoelectrons in the 100-1200 eV photon-energy range. A newly derived theoretical expression for nondipolar angular distributions characterizes the second-order effects using four new parameters with primary contributions from pure-quadrupole and octupole-dipole interference terms. Independent-particle calculations of these parameters account for a significant portion of the existing discrepancy between experiment and theory for Ne 2p first-order nondipole parameters.
authors.affiliation: Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.initials: A
authors.lastname: Derevianko
authors.initials: O
authors.lastname: Hemmers
authors.initials: S
authors.lastname: Oblad
authors.initials: P
authors.lastname: Glans
authors.initials: H
authors.lastname: Wang
authors.initials: SB
authors.lastname: Whitfield
authors.initials: R
authors.lastname: Wehlitz
authors.initials: IA
authors.lastname: Sellin
authors.initials: WR
authors.lastname: Johnson
authors.initials: DW
authors.lastname: Lindle