Polarized electrons were scattered elastically and inelastically from unpolarized thallium and lead atoms. The left-right scattering asymmetry has been measured for energies ranging from 2.5 to 14 eV at scattering angles between 35' and 125'. The influence of the electronic configuration of the valence electrons on the results of the asymmetry function is discussed. For elastic collisions no clear-cut conclusions about the significance of the 'fine-structure' effect compared with the Mott scattering effect can be drawn. Numerical results from R-matrix calculations show good agreement with the experimental data for thallium, whereas the theoretical predictions for lead are less satisfactory.
Ba3Pt4Al4 was prepared from the elements in niobium ampules and crystallizes in an orthorhombic structure, space group Cmcm (oP44, a = 1073.07(3), b = 812.30(3), c = 1182.69(3) pm) isopointal to the Zintl phase A2Zn5As4 (A = K, Rb). The structure features strands of distorted [Pt4Al4] heterocubane-like units connected by condensation over Pt/Al edges. These are arranged in a hexagonal rod packing by further condensation over Pt and Al atoms with the barium atoms located inside cavities of the [Pt4Al4](δ-) framework. Structural relaxation confirmed the electronic stability of the new phase, while band structure calculations indicate metallic behavior. Crystal orbital Hamilton bonding analysis coupled with Bader effective charge analysis suggest a polar intermetallic phase in which strong Al-Pt covalent bonds are present, while a significant electron transfer from Ba to the [Pt4Al4](δ-) network is found. By X-ray photoelectron spectroscopy measurements the Pt 4f5/2 and 4f7/2 energies for Ba3Pt4Al4 were found in the range of those of elemental Pt due to the electron transfer of Ba, while PtAl and PtAl2 show a pronounced shift toward a more cationic platinum state. (27)Al magic-angle spinning NMR investigations verified the two independent crystallographic Al sites with differently distorted tetrahedrally coordinated [AlPt4] units. Peak assignments could be made based on both geometrical considerations and in relation to electric field gradient calculations.
Polarized electrons were scattered from zinc, cadmium and indium atoms which were unpolarized. Elastic scattering asymmetries were observed at energies ranging from 0.3 (for Cd) to 14 eV and at angles from 30' to 125'. For indium inelastic scattering asymmetries were also measured. Comparing the asymmetries obtained from atoms with different electron configurations the authors discuss the influence of the atomic structure on spin-dependent electron scattering. In some cases the conclusions to be drawn are straightforward. For elastic scattering from indium comparison with theoretical data is required in order to disentangle the influence of the different mechanisms on the asymmetries.
The chirality-induced spin selectivity (CISS) effect
facilitates
a paradigm shift for controlling the outcome and efficiency of spin-dependent
chemical reactions, for example, photoinduced water splitting. While
the phenomenon is established in organic chiral molecules, its emergence
in chiral but inorganic, nonmolecular materials is not yet understood.
Nevertheless, inorganic spin-filtering materials offer favorable characteristics,
such as thermal and chemical stability, over organic, molecular spin
filters. Chiral cupric oxide (CuO) thin films can spin polarize (photo)electron
currents, and this capability is linked to the occurrence of the CISS
effect. In the present work, chiral CuO films, electrochemically deposited
on partially UV-transparent polycrystalline gold substrates, were
subjected to deep-UV laser pulses, and the average spin polarization
of photoelectrons was measured in a Mott scattering apparatus. By
energy resolving the photoelectrons and changing the photoexcitation
geometry, the energy distribution and spin polarization of the photoelectrons
originating from the Au substrate could be distinguished from those
arising from the CuO film. The findings reveal that the spin polarization
is energy dependent and, furthermore, indicate that the measured polarization
values can be rationalized as a sum of an intrinsic spin polarization
in the chiral oxide layer and a contribution via CISS-related spin
filtering of electrons from the Au substrate. The results support
efforts toward a rational design of further spin-selective catalytic
oxide materials.
A temperature induced valence phase transition from Yb3+ at higher temperatures to Yb2+ at lower temperatures was observed at T = 110(1) K for intermetallic YbPd2Al3.
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