Magnetic Dichroism in the Angular Distribution of Atomic Oxygen 2p Photoelectrons

A substantial difference in the angular distributions of 2p photoelectrons from polarized oxygen atoms was found for two antiparallel atomic polarizations. This magnetic dichroism was studied as a function of photon energy from 25 to 52 eV. Our method extends traditional photoelectron angular distribution measurements of open shell atoms to “complete” experiments in similar to spin-resolved measurements. The observed dichroism allows a determination of the dipole matrix elements for the εs and εd photoelectrons and their phase difference including the sign

Polarization correlations in the two--photon decay of hydrogen--like ions

Polarization properties of the photons emitted in the two-photon decay of hydrogen-like ions are studied within the framework of the density matrix and second-order perturbation theory. In particular, we derive the polarization correlation function that gives the probability of the (two-photon) coincidence measurement performed by polarization-sensitive detectors. Detailed calculations of this function are performed for the $2s_{1/2} \to 1s_{1/2}$ transition in neutral hydrogen as well as Xe$^{53+}$ and U$^{91+}$ ions. The obtained results allow us to understand the influence of relativistic and non-dipole effects on the polarization correlations in the bound-bound two-photon transitions in heavy ions

Interactions of polarized electrons and polarized photons with atoms and molecules

In this paper, we initially list 23 subfields of the research topics associated with the title of this paper. Then we present a detailed theoretical description of polarized–electron interactions with atoms and molecules. Spin effects based on Coulomb–direct, Coulomb–exchange and spin–orbit interactions in light and heavy atoms are described, and experimental data are presented as tests for relevant theoretical approximations. Electron–scattering interactions with orientated molecules such as CH3I and CH3Cl show interesting alignment and orientation effects, which are new types of test quantities for the theory of such electron–scattering processes with molecules. Numerous multielectron effects determine photoionization of atoms in general. Spin and spin–orbit interaction effects particularly can be studied by photoelectron spin experiments and by applying polarized atoms in the photoionization process. The former type of experiment has been used very successfully in the photoionization of rare gas atoms, while the latter type of experiment and related theories have been applied particularly for photoionization with partly filled subshells. Out of such photoionization experiments with polarized atoms we selected the one with oxygen atoms {O(1s22s22p4) 3P2+hν} for a more detailed description. While the photoionization process with unpolarized oxygen atoms is characterized by the cross–section, σ, and the angular distribution, β, only; a further parameter, β′, is required for photoionization with polarized oxygen atoms. Alternatively, it is possible to describe the photoionization of polarized oxygen atoms by deriving β and β′ from the ratio of two reduced matrix elements for s and d electrons and their relative phase difference