| 1. |
- Abelev, Betty, et al.
(author)
-
Long-range angular correlations on the near and away side in p-Pb collisions at root S-NN=5.02 TeV
- 2013
-
In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 719:1-3, s. 29-41
-
Journal article (peer-reviewed)abstract
- Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < P-T,P-assoc < P-T,P-trig < 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS Collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p(T) bins, and the widths show no significant evolution with event multiplicity or p(T). These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.
|
|
| 2. |
- Bounechada, Djamela, 1984, et al.
(author)
-
Mechanisms behind sulfur promoted oxidation of methane
- 2013
-
In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 15:22, s. 8648-8661
-
Journal article (peer-reviewed)abstract
- The promoting effect of SO2 on the activity for methane oxidation over platinum supported on silica, alumina and ceria has been studied by flow-reactor, in situ infrared spectroscopy and in situ high-energy x-ray diffraction experiments under transient reaction conditions. The catalytic activity is clearly dependent on the support material and its interaction with the noble metal both in absence and presence of sulfur. On platinum, the competitive reactant adsorption favors oxygen dissociation such that oxygen self-poisoning is observed for Pt/silica and Pt/alumina. Contrarily for Pt/ceria, no oxygen self-poisoning is observed, which seems to be due to additional reaction channels via sites on the platinum-ceria boundary and/or ceria surface considerably far from the Pt crystallites. Addition of sulfur dioxide generally leads to the formation of ad-SOx species on the supports with a concomitant removal and/or blockage/rearrangement of surface hydroxyl groups. Thereby, the methane oxidation is inhibited for Pt/silica, enhanced for Pt/alumina and temporary enhanced followed by inhibition after long-term exposure to sulfur for Pt/ceria. The observations can be explained by competitive oxidation of SO2 and CH4 on Pt/silica, formation of new active sites at the noble metal-support interface promoting dissociative adsorption of methane on Pt/alumina, and in the case of Pt/ceria, formation of promoting interfacial surface sulfates followed by formation of deactivating bulk-like sulfate species. Furthermore, it can be excluded that reduction of detrimental high oxygen coverage and/or oxide formation on the platinum particles through SO2 oxidation is the main cause for the promotional effects observed.
|
|
