Browsing by Department "University of St Andrews"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Crystal structure of [tris(4,4′-bipyridine)]diium bis(1,1,3,3-tetracyano-2-ethoxypropenide) trihydrate
    (2016) Setifi, Fatima; Valkonen, Arto; Setifi, Zouaoui; Nummelin, Sami; Touzani, Rachid; Glidewell, Christopher; Ferhat Abbas Sétif University 1; University of Jyväskylä; Department of Biotechnology and Chemical Technology; Mohammed First University of Oujda; University of St Andrews; Department of Bioproducts and Biosystems
    The title hydrated salt, C30H26N6 2+·2C9H5N4O-·3H2O, was obtained as an unexpected product from the hydrothermal reaction between potassium 1,1,3,3-tetracyano-2-ethoxypropenide, 4,4′-bipyridine and iron(II) sulfate heptahydrate. The cation lies across a twofold rotation axis in the space group I2/a with the other components all in general positions. In the cation, the H atom linking the pyridine units is disordered over two adjacent sites having occupancies of 0.66-(4) and 0.36-(4), i.e. as N - H⋯N and N⋯H - N. The water molecules of crystallization are each disordered over two sets of atomic sites, having occupancies of 0.522-(6) and 0.478-(6) for one, and 0.34-(3) and 0.16-(3) for the other, and it was not possible to reliably locate the H atoms associated with these partial-occupancy sites. In the crystal, four independent C - H⋯N hydrogen bonds link the ionic components into a three-dimensional network.
  • Thumbnail Image
    Item
    Crystal structures of 2,2′-bipyridin-1-ium 1,1,3,3-tetracyano-2-ethoxyprop-2-en-1-ide and bis(2,2′-bipyridin-1-ium) 1,1,3,3-tetracyano-2-(dicyano-methylene) propane-1,3-diide
    (2015-05-01) Setifi, Zouaoui; Valkonen, Arto; Fernandes, Manuel A.; Nummelin, Sami; Boughzala, Habib; Setifi, Fatima; Glidewell, Christopher; University Frères Mentouri - Constantine 1; University of Jyväskylä; University of the Witwatersrand; Department of Applied Physics; Université de Tunis El Manar; Ferhat Abbas Sétif University 1; University of St Andrews
    In 2,2′-bipyridin-1-ium 1,1,3,3-tetracyano-2-ethoxyprop-2-en-1-ide, C10H9N2+·-C9H5N4O-, (I), the ethyl group in the anion is disordered over two sets of atomic sites with occupancies 0.634 (9) and 0.366 (9), and the dihedral angle between the ring planes in the cation is 2.11 (7)°. The two independent C(CN)2 groups in the anion make dihedral angles of 10.60 (6) and 12.44 (4)° with the central propenide unit, and the bond distances in the anion provide evidence for extensive electronic delocalization. In bis(2,2′-bipyridin-1-ium) 1,1,3,3-tetra-cyano-2-(dicyanomethylene) propane-1,3-diide [alternative name bis(2,2′-bipyr-idin-1-ium) tris(dicyanomethylene) methanediide], 2C10H9N2+·C10N62- (II), the dihedral angles between the ring planes in the two independent cations are 7.7 (2) and 10.92 (17)°. The anion exhibits approximate C3 symmetry, consistent with extensive electronic delocalization, and the three independent C(CN)2 groups make dihedral angles of 23.8 (2), 27.0 (3) and 27.4 (2)° with the central plane. The ions in (I) are linked by an N - H⋯N hydrogen bond and the resulting ion pairs are linked by two independent C - H⋯N hydrogen bonds, forming a ribbon containing alternating R44(18) and R44(26) rings, where both ring types are centrosymmetric. The ions in (II) are linked by two independent N - H⋯N hydrogen bonds and the resulting ion triplets are linked by a C - H⋯N hydrogen bond, forming a C12(7) chain containing anions and only one type of cation, with the other cation linked to the chain by a further C - H⋯N hydrogen bond.
  • Thumbnail Image
    Item
    Evolution of Temporal Coherence in Confined Exciton-Polariton Condensates
    (2018-01-05) Klaas, M.; Flayac, H.; Amthor, M.; Savenko, I. G.; Brodbeck, S.; Ala-Nissila, T.; Klembt, S.; Schneider, C.; Hoefling, S.; University of Würzburg; Swiss Federal Institute of Technology Lausanne; Institute for Basic Science; Centre of Excellence in Quantum Technology, QTF; University of St Andrews; Department of Applied Physics
    We study the influence of spatial confinement on the second-order temporal coherence of the emission from a semiconductor mieroeavity in the strong coupling regime. The confinement, provided by etched micropillars, has a favorable impact on the temporal coherence of solid state quasicondensates that evolve in our device above threshold. By fitting the experimental data with a microscopic quantum theory based on a quantum jump approach, we scrutinize the influence of pump power and confinement and find that phonon-mediated transitions are enhanced in the case of a confined structure, in which the modes split into a discrete set. By increasing the pump power beyond the condensation threshold, temporal coherence significantly improves in devices with increased spatial confinement, as revealed in the transition from thermal to coherent statistics of the emitted light.
  • Thumbnail Image
    Item
    Millimeter wave imaging at up to 40 frames per second using an optoelectronic photo-injected Fresnel zone plate lens antenna
    (SPIE, 2016-01-01) Robertson, Duncan A.; Gallacher, Thomas F.; Søndenå, Rune; Macfarlane, David G.; University of St Andrews; Department of Radio Science and Engineering; Institute for Energy Technology; Department of Electronics and Nanoengineering; Wikner, David A.; Luukanen, Arttu R.
    Optoelectronic methods are promising for rapid and highly reconfigurable beam steering across the microwave to the terahertz range. In particular, the photo-injected Fresnel zone plate antenna (piFZPA) offers high speed, wide angle, precise beam steering with good beam quality, to enable video rate millimeter wave imagery with no moving parts. We present a piFZPA demonstrator based on a commercial digital light projector (DLP) and high power laser which achieves steering rates up to 17,500 beams per second at 94 and 188 GHz. We also demonstrate radar imaging at 94 GHz at frame rates of 40 Hz (2D PPI) and 7 Hz (3D volumetric).