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Articles you may be interested inElectron induced dissociation of trimethyl (methylcyclopentadienyl) platinum (IV): Total cross section as a function of incident electron energy Adsorption and reaction of methanol on clean and oxygen modified rhodium/vanadium surface alloys Line of sight ͑LOS͒ techniques comprise those methods in which species emanating from a surface ͑atoms, molecules, and radicals͒ undergo just a single pass through the ionization volume of a mass spectrometer before being pumped. This is achieved by enclosing the mass spectrometer within a cryoshield fitted with appropriate apertures, such that line of sight is established only between a patch on the sample surface ͑Ϸ7 mm diameter͒ and the ionization volume. All LOS techniques are free from extraneous signals and have approximately equal detection probabilities for all species. Line of sight temperature programmed desorption, sticking probability ͑LOSSP͒, and product desorption ͑LOSPD͒ provide powerful and reliable ways of studying all aspects of surface kinetics, by allowing an inventory of all species arriving at and departing from a surface, for any combination of partial pressures, surface temperature, surface composition, and surface structure. Here we illustrate LOSSP and LOSPD using the reactions of 1-bromo-2-chloroethane, BrCH 2 CH 2 Cl,͑BCE͒ and iodotrifluoromethane, CF 3 I, on Cu͑111͒. For BCE we show that there is a 1:1 correspondence of product ethene to reactant BCE during dissociative adsorption at TϾ253 K, and that the dissociative adsorption is nonactivated with a transition state 11Ϯ2.5 kJ mol Ϫ1 below zero ͑0ϭmolecule at infinity͒. For CF 3 I dissociative adsorption occurs at room temperature with a sticking probability of 0.96Ϯ0.02 to produce CF 2 • which can either desorb as gaseous CF 2 • radicals ͑observed͒ or undergo a coupling reaction and then desorb as gaseous C 2 F 4 ͑also observed͒. No other gas phase products were observed.

International audienceFor the first time, subelectron readout noise has been achieved with a camera dedicated to astronomical wavefront-sensing applications. The OCam system demonstrated this performance at a 1300 Hz frame rate and with 240 x 240 pixel frame size. ESO and JRA2 OPTICON jointly funded e2v Technologies to develop a custom CCD for adaptive optics (AO) wavefront-sensing applications. The device, called CCD220, is a compact Peltier-cooled 240 x 240 pixel frame-transfer eight-output back-illuminated sensor using the EMCCD technology. This article demonstrates, for the first time, subelectron readout noise at frame rates from 25 Hz to 1300 Hz and dark current lower than 0.01 e(-) pixel(-1) frame(-1). It reports on the quantitative performance characterization of OCam and the CCD220, including readout noise, dark current, multiplication gain, quantum efficiency, and charge transfer efficiency. OCam includes a low-noise preamplifier stage, a digital board to generate the clocks, and a microcontroller. The data acquisition system includes a user-friendly timer file editor to generate any type of clocking scheme. A second version of OCam, called OCam(2), has been designed to offer enhanced performance, a completely sealed camera package, and an additional Peltier stage to facilitate operation on a telescope or environmentally challenging applications. New features of OCam(2) are presented in this article. This instrumental development will strongly impact the performance of the most advanced AO systems to come

Adatoms immersed in an x-ray standing wave at a surface betray their position within the wave by the way they absorb the x-rays; feebly when positioned at the nodes, strongly when positioned at the antinodes. The elemental (and chemical) identity of the adatoms are easily monitored using the binding energies of the photoelectron or Auger electron emissions, while the intensities of these emissions provide the information needed to determine the atomic positions relative to the crystalline substrate which formed the standing wave. By using normal incidence Bragg diffraction to generate the standing wave, the technique is applicable to the rather imperfect crystalline samples and standard manipulators used in most surface science studies. Examples of structural studies from a range of systems will be drawn from recent work carried out at the SRS in Daresbury to illustrate the strengths, and weaknesses, of this structural technique. Specifically, the structure of reactive intermediates (SiHx) formed by chemical reaction of silane on Cu(111); the structure of a physisorbed molecule (ClCH2CH2F) on Cu(111); an example of how chemically shifted Auger peaks may be useful for chemical shift XSW (chloroform on a chlorinated copper surface), and a system which presents many difficulties when studied by this technique, methyl thiolate on Au(111).

ESO and JRA2 OPTICON have funded e2v technologies to develop a compact packaged Peltier cooled 24 µm square 240x240 pixels split frame transfer 8-output back-illuminated L3Vision CCD3, L3Vision CCD for Adaptive Optic Wave Front Sensor (AO WFS) applications. The device is designed to achieve sub-electron read noise at frame rates from 25 Hz to 1,500 Hz and dark current lower than 0.01 e-/pixel/frame. The development has many unique features. To obtain high frame rates, multi-output EMCCD gain registers and metal buttressing of row clock lines are used. The baseline device is built in standard silicon. In addition, a split wafer run has enabled two speculative variants to be built; deep depletion silicon devices to improve red response and devices with an electronic shutter to extend use to Rayleigh and Pulsed Laser Guide Star applications. These are all firsts for L3Vision CCDs. The designs of the CCD and Peltier package have passed their reviews and fabrication has begun. This paper will describe the progress to date, the requirements and the design of the CCD and compact Peltier package, technology trade-offs, schedule and proposed test plan. High readout speed, low noise and compactness (requirement to fit in confined spaces) provide special challenges to ESO's AO variant of its NGC, New General detector Controller to drive this CCD. This paper will describe progress made on the design of the controller to meet these special needs.