Chemistry, Physics & Earth Sciences

Permanent URI for this community

https://hdl.handle.net/2328/2961

Publications produced by staff from the School of Chemistry, Physics & Earth Sciences.

Browse

Browsing Chemistry, Physics & Earth Sciences by Issue Date

Jump to a point in the index:
Now showing 1 - 20 of 158
  • Item
    Influence of a partially oxidized calcium cathode on the performance of polymeric light emitting diodes
    (American Institute of Physics, 2001) Andersson, Gunther ; de Jong, M P ; Janssen, F J J ; Sturm, J M ; van Ijzendoorn, L J ; Denier van der Gon, A W ; de Voigt, M J A ; Brongersma, H H
    We investigated the influence of the presence of oxygen during the deposition of the calcium cathode on the structure and on the performance of polymeric light emitting diodes (pLEDs). The oxygen background pressure during deposition of the calcium cathode of polymeric LEDs was varied. Subsequently, the oxygen depth distribution was measured and correlated with the performance of the pLEDs. The devices have been fabricated in a recently built ultraclean setup. The polymer layers of the pLEDs have been spincoated in a dry nitrogen atmosphere and transported directly into an ultrahigh vacuum chamber where the metal electrodes have been deposited by evaporation. We used indium–tin–oxide as anode, OC1C10 PPV as electroluminescent polymer, calcium as cathode, and aluminum as protecting layer. We achieved reproducibility of about 15% in current and brightness for devices fabricated in an oxygen atmosphere of less than or equal to 10 -9 mbar. For further investigations the calcium deposition was carried out in an oxygen atmosphere from 10 -8 to 10 -5 mbar. We determined the amount of oxygen in the different layers of the current–voltage-light characterized pLEDs with elastic recoil detection analysis and correlated it with the characteristics of the devices. The external efficiency of the pLEDs decreases continuously with increasing oxygen pressure, the current shows a pronounced minimum. The brightness mostly decreases with increasing oxygen with an indication of a slight minimum. PLEDs with completely oxidized calcium are not operational. The first contact of the pLEDs with the dry glove box environment leads to an immediate reduction of current and brightness which is caused by the cooling of the devices by several degrees. Determining reproducible characteristics of pLEDs in the vacuum requires the measurement of their temperature.
  • Item
    Norbornane: An investigation into its valence electronic structure using electron momentum spectroscopy, and density functional and Green's function theories
    ( 2004) Winkler, D A ; Newell, W R ; Nixon, Kate Louise ; Wang, F ; Trout, Neil Alan ; Maddern, Todd Michael ; Campbell, Laurence ; Brunger, Michael James ; Knippenberg, S ; Deleuze, M ; Francois, J-P
  • Item
    Infrared Auroral Emissions Driven by Resonant Electron Impact Excitation of NO molecules
    ( 2004) Campbell, Laurence ; Brunger, Michael James ; Buckman, Stephen J ; Jelisavcic, M ; Petrovic, Z L ; Panajotovic, R
  • Item
    Monitoring EDTA and endogenous metabolite biomarkers from serum with mass spectrometry
    (Hindawi, 2005) Lowe, Rachel D ; Go, Eden P ; Tong, Grace C ; Voelcker, Nicolas Hans ; Siuzdak, Gary
    We describe a quantitative method for the determination of ethylenediaminetetraacetic acid (EDTA) in human serum by gas chromatography mass spectrometry (GC-MS), liquid chromatography electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS), and desorption ionisation on silicon mass spectrometry (DIOS-MS). In the initial stages of the analysis, endogenous metabolites (1-palmitoyl-sn-glycero-3-phosphocholine and 1-stearoyl-sn-glycero-3-phosphocholine) were readily observed in LC-ESI-MS and DIOS-MS however, direct analysis of the EDTA free acid had limited sensitivity. In order to improve EDTA detection we employed a straightforward esterification derivatization. The most successful derivatization procedure converted EDTA to its methyl ester and, since 13C isotopes of these reagents are readily available, internal standards could be easily generated for quantitative analysis. This approach provided a limit of detection of 0.5 and 0.1 μM for GC-MS and LC-ESI-MS, and offers a viable method for the EDTA detection.
  • Item
    Electron Collisions in our Atmosphere - How the Microscopic Drives the Macroscopic
    (American Institute of Physics, 2005) Buckman, Stephen J ; Brunger, Michael James ; Campbell, Laurence ; Jelisavcic, M ; Petrovic, Z L
  • Item
    Role of electronic excited N2 in vibrational excitation of the N2 ground state at high latitudes
    ( 2006) Campbell, Laurence ; Cartwright, D C ; Brunger, Michael James ; Teubner, Peter John
  • Item
    Role of excited nitrogen in the ionosphere
    (American Institute of Physics, 2006) Campbell, Laurence ; Brunger, Michael James ; Cartwright, D C ; Bolorizadeh, Mohammad Agha
  • Item
    Role of excited N2 in the production of nitric oxide
    ( 2007) Campbell, Laurence ; Cartwright, D C ; Brunger, Michael James
  • Item
    Closed-form expressions for state-to-state charge-transfer differential cross sections in a modified Faddeev three-body approach
    ( 2007) Ghanbari Adivi, E ; Brunger, Michael James ; Bolorizadeh, Mohammad Agha ; Campbell, Laurence
  • Item
    Electron-impact excitation of the B1[Sigma]+u and C1[Pi]u electronic states of H2
    ( 2008) Brunger, Michael James ; Kato, H ; Kawahara, H ; Hoshino, M ; Tanaka, Hiroshi ; Campbell, Laurence
  • Item
    Carbon dioxide electron cooling rates in the atmospheres of Mars and Venus
    ( 2008) Campbell, Laurence ; Brunger, Michael James ; Rescigno, T N
  • Item
    Electron cooling by carbon monoxide in the atmospheres of Mars and Venus
    (BioMed Central - http://www.biomedcentral.com, 2008-02-04) Campbell, Laurence ; Brunger, Michael James
    Electron cooling, in which free electrons lose energy to vibrational excitation of gases, has been identified as a significant process in the atmospheres of Mars and Venus for electron impact on CO2. This process does not appear to have been evaluated for CO, although the density of CO exceeds that of CO2 in the upper atmospheres of these planets. In this paper electron cooling rates for CO are calculated and compared with existing rates for CO2. It is found that electron cooling by CO becomes more significant than by CO2 above altitudes of about 300 km on Mars and about 168 km on Venus. The sensitivity of the calculated cooling rates to different measurements of the integral cross sections for electron-impact vibrational excitation of CO is also investigated.
  • Item
    Integral cross sections for electron-impact excitation of the 4 2P state in copper
    (The American Physical Society, 2009) Suvorov, V ; Teubner, Peter John ; Karaganov, Victor ; Ratnavelu, K ; Zhou, Y ; Brunger, Michael James
    We report integral cross sections for electron-impact excitation of the 4 2P state in copper for incident electrons with energies in the range from threshold to 100 eV. Measurements, based on an optical excitation function procedure, are compared with coupled-channel and coupled-channel-optical method calculations that we have also performed as a part of this study. Agreement between our measurements and theory was generally only modest. The present measurements are also found to be in quite good accord with the early near-threshold integral cross sections of Flynn et al. and the higher energy measurements from Ismail and Teubner. Where possible, comparison of our data is also made with earlier theory.
  • Item
    Total cross sections for positron scattering from H2 at low energies
    (The American Physical Society, 2009) Zecca, Antonio ; Chiari, Luca ; Sarkar, Anindya ; Nixon, Kate Louise ; Brunger, Michael James
    This paper revisits positron scattering from molecular hydrogen, in an attempt to provide accurate total cross-section data against which theoretical calculations might be benchmarked. The present data were measured over the energy range 0.1–50 eV and, where possible, are compared to results from previous experiments and calculations. Agreement with the earlier data was typically very good at energies above 10 eV but becomes progressively more marginal as we go to lower energies. None of the current theories quantitatively reproduce our measurements over the entire energy range, although at a qualitative level the main features driving the scattering dynamics are apparent.
  • Item
    Onset of carbon-carbon bonding in the Nb5Cy (y = 0-6) clusters: a threshold photo-ionisation and density functional theory study
    (Royal Society of Chemistry, 2009) Dryza, Viktoras ; Gascooke, Jason ; Buntine, Mark A ; Metha, Gregory Francis
    We have used photo-ionisation efficiency spectroscopy to determine the ionisation potentials (IPs) of the niobium–carbide clusters, Nb5Cy (y = 0–6). Of these clusters Nb5C2 and Nb5C3 exhibit the lowest IPs. Complementary density functional theory calculations have been performed to locate the lowest energy isomers for each cluster. By comparing the experimental IPs with those calculated for candidate isomers, the structures of the Nb5Cy clusters observed in the experiment are inferred. For all these structures, the underlying Nb5 cluster has either a ‘prolate’ or ‘oblate’ trigonal bipyramid geometry. Both Nb5C5 and Nb5C6 are shown to contain carbon–carbon bonding in the form of one and two molecular C2 units, respectively.
  • Item
    Using a fully coupled surface water - groundwater model to quantify streamflow components
    (Modelling and Simulation Society of Australia and New Zealand, 2009) Partington, Dan J ; Werner, Adrian D ; Brunner, Philip Andreas ; Simmons, Craig Trevor ; Dandy, Graeme C ; Maier, Holger R
    Separation of streamflow components into quickflow and baseflow is usually carried out in two main ways: hydrograph recession analysis and tracer-based methods. In this paper, it is proposed to use a fully coupled surface and subsurface flow and transport model to gain a better understanding of the relationship between physical catchment characteristics (e.g. aquifer hydraulic conductivity) and hydrological response (e.g. stream salinity and flow response) to a rainfall event. This enables an evaluation of the common empirical approaches of recession analysis and baseflow separation in practice. This is achieved by conducting a range of numerical experiments on a hypothetical case study, which is based on a commonly used surface water-groundwater interaction benchmarking problem. A fully coupled, variably saturated surface-subsurface flow and transport model (HydroGeoSphere) forms the basis of the numerical experiments conducted in this investigation. The results indicate that the empirical baseflow separation algorithms failed to reproduce the simulated groundwater discharge to the stream from the theoretical catchment, although it was identified that the surface-subsurface benchmark problem needs to be further developed to produce more realistic hydrograph behaviour before a proper comparison between the two approaches can be made.
  • Item
    Regional GHS implementation strategy for ASEAN
    (Institut Kimia Malaysia, 2009) Choo Ta, Goh ; Bin Mokhtar, Mazlin ; Peterson, Peter John ; Bin Yahaya, Nadzri
    It is essential for the safe use of chemicals to classify them according to their hazards. Different degrees of hazard must be identified based on specific cut-off values. After chemicals have been classified, they should be labelled accordingly and this hazard information must be sufficiently communicated to the chemical transporters, storekeepers, distributors, users and regulatory authorities. At the United Nations Conference on Environment and Development (UNCED) held in 1992 in Brazil, the establishment of a globally harmonized hazard classification and compatible labelling system (GHS) was adopted. A study was conducted to assess GHS capacity at the ASEAN regional level, and an implementation strategy has been developed. Two strategies are proposed, namely a sectoral strategy that focuses on four thematic sectors - industrial workplace, agriculture, transport and consumer products respectively; and a cross-sectoral strategy for GHS implementation in ASEAN.
  • Item
    Differential and integral cross sections for elastic electron scattering from CF2
    (The American Physical Society, 2009) Francis-Staite, Jessica ; Maddern, Todd Michael ; Brunger, Michael James ; Buckman, Stephen J ; Winstead, Carl ; McKoy, Vincent ; Bolorizadeh, Mohammad Agha ; Cho, Hyuck
    We report the results of measurements and calculations of differential and integral cross sections for elastic electron scattering from the CF2 molecular radical. The energy range of the present investigation was 2–20 eV, while the angular distributions were measured at specific angles within the scattered electron range 20°–135°. The calculations employed the Schwinger multichannel method and were carried out both in the static-exchange and static-exchange plus polarization (SEP) approximations, with generally quite good agreement found between the data and the SEP level results. This was particularly true at lower energies, illustrating the importance of correctly accounting for the polarization in these collisions.
  • Item
    Measuring the internal energy content of molecules transported across the liquid-gas interface
    (IOP Publishing, 2009) Maselli, Olivia J ; Gascooke, Jason ; Lawrance, Warren Donald ; Buntine, Mark A
    Many details concerning the mechanism associated with the liberation of molecules from a liquid surface remain to be elucidated. We use the liquid microjet technique coupled with laser spectroscopy to measure the rotational and vibrational energy content of benzene spontaneously evaporating from a water-ethanol solution. These measurements provide molecular level insight into the mass and energy transfer process associated with evaporation.
  • Item
    Electron-scattering cross sections for collisions with tetrahydrofuran from 50 to 5000 eV
    (The American Physical Society, 2009) Fuss, Martina C ; Munoz, Antonio ; Oller, Juan Carlos ; Blanco, Francisco ; Almeida, Diogo ; Limao-Vieira, Paulo ; Do, Thi Phuong Thao ; Brunger, Michael James ; Garcia, Gustavo
    In this paper, we report on total electron tetrahydrofuran (C4H8O) scattering cross-section measurements for energies in the range from 50 to 5000 eV with experimental errors of about 5%. In addition, integral elastic and inelastic cross sections have been calculated over a broad energy range (1–10 000 eV), with an optical potential method assuming a screening-corrected independent atom representation. Partial and total ionization cross sections have been also obtained by combining simultaneous electron and ion measurements with a time-of-flight analysis of the ionic induced fragmentation. Finally, an average energy distribution of secondary electrons has been derived from these measurements in order to provide data for modeling electron-induced damage in biomolecular systems.