title: Experimental verification of quadrupole-dipole interference in spin-resolved photoionization.
abstract: We have measured the spin polarization of Xe (4p)(-1) photoelectrons after ionization with circularly polarized light at photon energies close to the ionization threshold where a resonant enhancement of quadrupole transitions has recently been predicted. At a reaction angle of 90 degrees a nonvanishing longitudinal spin polarization component of about 4% clearly indicates a quadrupole contribution to the photoexcitation. This is the first experimental evidence for the influence of nondipole transitions on the photoionization process at excitation energies much below 1 keV in an observable other than the intensity angular distribution.
authors.affiliation: Universität Bielefeld, Fakultät für Physik, Universitätsstrasse 25, 33615 Bielefeld, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Khalil
authors.forename: B
authors.initials: B
authors.lastname: Schmidtke
authors.forename: M
authors.initials: M
authors.lastname: Drescher
authors.forename: N
authors.initials: N
authors.lastname: Müller
authors.forename: U
authors.initials: U
authors.lastname: Heinzmann