Circular Dichroism in Cu Resonant Auger Electron Diffraction

Abstract

Upon a core level excitation by circularly polarized light (CPL), the angular momentum of light, i.e. helicity, is transferred to the emitted photoelectron. This phenomenon can be confirmed by the parallax shift measurement of the forward focusing peak (FFP) direction in a stereograph of the atomic arrangement. The angular momentum of the emitted photoelectron is the sum of CPL helicity and the magnetic quantum number (MQN) of the initial state that define the quantum number of the core hole final state. The core hole may decay via Auger electron emission, where in this two electron process the angular momentum has to be conserved as well. Starting from a given core hole, different Auger decay channels with different final state energies and angular momenta of the emitted Auger electrons may be populated. Here we report the observation and formulation of the angular momentum transfer of light to Auger electrons, instead of photoelectrons. We measured photoelectron and Auger electron intensity angular distributions from Cu(111) and Cu(001) surfaces as a function of photon energy and photoelectron kinetic energy. By combining Auger electron spectroscopy with the FFP shift measurements at absorption threshold, element-and MQN-specific hole states can be generated in the valence band. Abstract: Upon a core level excitation by circularly polarized light (CPL), the angular momentum of light, i.e. helicity, is transferred to the emitted photoelectron. This phenomenon can be confirmed by the parallax shift measurement of the forward focusing peak (FFP) direction in a stereograph of the atomic arrangement. The angular momentum of the emitted photoelectron is the sum of CPL helicity and the magnetic quantum number (MQN) of the initial state that define the quantum number of the core hole final state. The core hole may decay via Auger electron emission, where in this two electron process the angular momentum has to be conserved as well. Starting from a given core hole, different Auger decay channels with different final state energies and angular momenta of the emitted Auger electrons may be populated. Here we report the observation and formulation of the angular momentum transfer of light to Auger electrons, instead of photoelectrons. We measured photoelectron and Auger electron intensity angular distributions from Cu(111) and Cu(001) surfaces as a function of photon energy and photoelectron kinetic energy. By combining Auger electron spectroscopy with

Parallel and antiparallel angular momentum transfer of circularly polarized light to photoelectrons and Auger electrons at the Ni L3 absorption threshold

“…The polar angle (θ ) dependences of p to d and d to f transition probabilities were calculated and shown elsewhere [22]. spiral [30].…”

“…Recently, a prominent FFP ACD was also found in the Auger electron intensity angular distribution at the absorption threshold [20][21][22]. Extraordinary large angular momentum transfer to the resonant Auger electron where the excited core electron is trapped at conduction-band state was found by Morscher et al [20] for Ni L 2 absorption and showed that the surface magnetization orientation can be determined in three dimensions.…”

“…We reported a quantitative analysis of angularmomentum-polarized LM 4,5 M 4,5 Auger electrons from the nonmagnetic Cu surfaces at the L 3 and L 2 absorption thresholds and showed that the amount of angular momentum transfer depends on the term of the two-hole final state [21,22]. The amplitude and the direction of angular momentum transfer depend largely on the kinds of atomic orbitals involved in the Auger decay process.…”