Spin-resolved triple differential (e, 2e) cross sections have been measured for ionization of xenon atoms by polarized electrons for energies between 40 and 200 eV. Significant spin up-down asymmetries in the (e, 2e) cross sections have been obtained at all energies. These are dominated by the interplay of orbital orientation, fine-structure interaction and exchange of the colliding electrons ('fine-structure effect'), whereas the influence of relativistic orbitals and of the continuum spin-orbit interaction is less important. The results are compared with recent DWBA calculations that include exchange with the electrons of the residual ion (exchange distortion), and satisfactory agreement is found. In particular, the discrepancies between theory and experiment at 40 eV and symmetric energy sharing are resolved.
The atomic orientation J⊥+ generated by polarized-electron impact excitation of Hg (6s2)1S0 → (6s6p)3P1 is studied using the electron–photon coincidence technique. J⊥+ shows a significant dependence on the spin projection of the incident electrons. Experimental results are compared with theoretical predictions employing a semi-relativistic five-state R-matrix (close-coupling) description and the relativistic distorted-wave approximation. The experimental data show, in qualitative agreement with the calculations, that the well established orientation propensity rules for light atoms are apparently violated if the electron spin is initially down with respect to the scattering plane. The applicability of the propensity rules to electron-impact excitation of heavy atoms is analysed. The observed apparent violation is attributed to a quantum mechanical interference caused by ‘intermediate coupling’ within the excited state. A re-evaluation of the data supports the validity of the orientation propensity rules.
For the mercury 6s6p 1P1 and 6s6p 3P1 states excited by electron impact, the linear polarization of the light emitted in the transition to the ground state has been measured from threshold to intermediate energy for the decay photons of 254 and 185 nm wavelength, respectively. The results for both lines are in surprisingly good agreement with a calculation based on the Born-Ochkur approximation, neglecting spin-orbit terms for the continuum electron but allowing for electron exchange effects and intermediate coupling.
The atomic orientation J⊥+ generated by polarized-electron impact excitation of Pb(6p2)3P0 → (6p7s)3P1 is studied experimentally using the electron–photon coincidence technique. For the decay transition (6p7s)3P1 → (6p2)3P2, the connection between the polarization components of the emitted photons and the coherence parameters J⊥+, Pl+, γ, h is given. J⊥+ shows a significant dependence on the spin projection of the incident electrons with an energy of 6 eV. The experimental results are compared with theoretical predictions from a semi-relativistic Breit–Pauli R-matrix model and the relativistic distorted-wave approximation and are interpreted with regard to well-established orientation propensity rules. The experimental data show, in agreement with the calculation and the prediction made by a semi-classical trajectory model, that the propensity rules hold for the excitation of the relatively heavy lead atom.
The design of a compact multiangle electron analyzer array for simultaneous detection of scattered and ejected electrons at nine different angles is described. It consists of eight slim "simulated" cylindrical mirror analyzers (CMAs) providing electron detection for scattering/ejected angles of 14 degrees apart from each other. A ninth analyzer is arranged to a scattering angle on the opposite side. A single analyzer has cylindrical symmetry equipotential lines in the region of the beam trajectories, whereas its electrodes are noncylindrical, except for the inner cylinder. The new spectrometer is easy to build because only a few electrodes of simple shape are needed for each of the analyzers. The electron optical properties of the new device are very close to those of a true CMA. Its geometric width, however, is only less than one-fifth of that of a conventional CMA, which allows one to arrange several analyzers close to each other. Example results with the new device are presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.