Oxygen on Fe(100) and Fe(110)

Investigations of the electronic and magnetic properties of oxygen adsorbed on magnetized iron films have been carried out by means of angle and spin resolving photoelectron spectroscopy. Iron, epitaxially grown on W(100) and W(110) crystals, served as the ferromagnetic substrate. Exchange splittings of the O 2p_x derived level have been detected, demonstrating a magnetic coupling between the chemisorbate and the iron layer. Variations of the exchange splitting have occurred as a function of the oxygen coverage, photon energy, and emission angle. High oxygen exposures have lead to a FeO overlayer at the surface.     

Multiscale Finite Element Modeling of Arc Dynamics in a DC Plasma Torch

The dynamics of the electric arc inside a direct current non-transferred arc plasma torch are simulated using a three-dimensional, transient, equilibrium model. The fluid and electromagnetic equations are solved numerically in a fully coupled approach by a multiscale finite element method. Simulations of a torch operating with argon and argon–hydrogen under different operating conditions are presented. The model is able to predict the operation of the torch in steady and takeover modes without any further assumption on the reattachment process except for the use of an artificially high electrical conductivity near the electrodes, needed because of the equilibrium assumption. The results obtained indicate that the reattachment process in these operating modes may be driven by the movement of the arc rather than by a breakdown-like process. It is also found that, for a torch operating in these modes and using straight gas injection, the arc will tend to re-attach to the opposite side of its original attachment. This phenomenon seems to be produced by a net angular momentum on the arc due to the imbalance between magnetic and fluid drag forces.     

Direct fission versus sequential evaporation mechanism of sputtered caesium iodide cluster ions

A triple stage hybrid mass spectrometer was scanned for the trapping of the reaction intermediates of the over-all loss of two CsI-moieties from size-selected caesium iodide cluster ions of the general formula Cs (CsI)⁺ _n . In addition to appropriate MS/MS/MS-methods an electrically floated collision cell has been applied to trap intermediates of unimolecular and collision-induced evaporations. In comparison with other experimental findings the features of the evaporation mechanism are discussed.     

2-Phosphinophenolate complexes: formation and crystal structure of a novel trinuclear mu-O nickel(II)-tris(P(intersection)O-chelate)

A novel linear trinuclear mu-O-bridging 2-phosphinophenolate nickel(II) complex with fac-tris(P(intersection)O- chelates) in the terminal positions and the three oxygen atoms each facing the central nickel(II) cation was synthesized and structurally characterized by X-ray crystallography. To the best of our knowledge, this is the first example of an octahedral Ni(II) tris(P(intersection)O- chelate).     

Direct optical emission spectroscopy of liquid analytes using an electrolyte as a cathode discharge source (ELCAD) integrated on a micro-fluidic chip

Atomic emission detection of metallic species in aqueous solutions has been performed using a miniaturised plasma created within a planar, glass micro-fluidic chip. Detection was achieved using an Electrolyte as a Cathode Discharge source (ELCAD) in which the sample solution itself is used as the cathode for the discharge. To realise the ELCAD technique within a micro-fluidic device, a parallel liquid-gas flow was set up in a micro-channel and a glow discharge ignited between the flowing liquid sample surface and a metal wire anode. The detection of copper and sodium was achieved, using atmospheric pressure air as a carrier gas, by observation of atomic emission lines of copper at 324 nm, 327 nm, 511 nm, 515 nm and 522 nm and an atomic emission line of sodium at 589 nm using a commercially available miniaturised spectrometer. A total electrical power of less than 70 mW was required to sustain the discharge. A semi-quantitative, absolute detection limit of 17 nmol s(-1) was obtained for sodium with a sample flow rate of 100 microL min(-1) and an integration time of 100 ms in air at atmospheric pressure. The volume required for such detection is approximately 170 nL. Further analysis was performed with an Echelle spectrometer using both argon and air as a carrier gas. The geometry and flow rates used demonstrate the feasibility of integrating such micro-plasmas into other micro-fluidic devices, such as miniaturised CE devices, as a method of detection. The potential for using such micro-plasmas within highly portable miniaturised systems and mu-TAS devices is presented and discussed.     

A Three-Dimensional Two-Phase Model for Thermal Plasma Chemical Vapor Deposition with Liquid Feedstock Injection

In this paper, a comprehensive model for thermal plasma chemical vapor deposition (TPCVD) with liquid feedstock injection is documented. The gas flow is assumed to be steady, of a single temperature. Radiation and charged species contributions are excluded, but extensive homogeneous and heterogeneous chemistry is included. The liquid phase is traced by considering individual droplets. Discussion on the model's application to diamond production from acetone in a hydrogen–argon plasma is included. The major conclusions are: (1) Liquid injection possesses a capability to deliver the hydrocarbon precursor directly onto the deposition target. (2) For the case of complete evaporation of the droplet before reaching the substrate, the deposition rate is similar to that obtained with gaseous precursors. (3) The computational results compare well with experimental data. The modeling results can be used to optimize the injection parameters with regard to the deposition rate.