A perfectly stoichiometric and flat CeO2(111) surface on a bulk-like ceria film.

In surface science and model catalysis, cerium oxide (ceria) is mostly grown as an ultra-thin film on a metal substrate in the ultra-high vacuum to understand fundamental mechanisms involved in diverse surface chemistry processes. However, such ultra-thin films do not have the contribution of a bulk ceria underneath, which is currently discussed to have a high impact on in particular surface redox processes. Here, we present a fully oxidized ceria thick film (180 nm) with a perfectly stoichiometric CeO2(111) surface exhibiting exceptionally large, atomically flat terraces.

Photochemistry of carbon monoxide and methanol in water and nitric acid hydrate ices: A NEXAFS study.

Soft X-ray induced chemistry of H(2)O, CO and CH(3)OH and the effects of the water and nitric acid hydrate (HNO(3).1.65H(2)O) matrix on the photochemistry of CO and CH(3)OH have been investigated using NEXAFS spectroscopy.

The irradiation of ammonia ice studied by near edge x-ray absorption spectroscopy.

A vapor-deposited NH(3) ice film irradiated at 20 K with 150 eV photons has been studied with near-edge x-ray absorption fine structure (NEXAFS) spectroscopy at the nitrogen K-edge. Irradiation leads to the formation of high amounts (12%) of molecular nitrogen N(2), whose concentration as a function of the absorbed energy has been quantified to 0.13 molecule/eV.

Preliminary study of the influence of environment conditions on the successive hydrogenations of CO.

The successive hydrogenation of CO has been investigated by two methods. The first is hydrogenation of a CO surface. The second is co-injection of CO molecules and H atoms.

Influence of water in the UV-induced chemistry of methanol in the solid phase.

UV-irradiated methanol (CH3OH) in water ice at 3 K has been investigated with infrared spectroscopy and compared with pure methanol. The main byproducts detected are formaldehyde (H2CO), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and ethylene glycol (C2H4(OH)2). The production of H2CO, CO2, and CO is enhanced in water ice, resulting from cross reactions between the byproducts of methanol with those of water (OH and H2O2).

Radiation effects in water ice: a near-edge x-ray absorption fine structure study.

The changes in the structure and composition of vapor-deposited ice films irradiated at 20 K with soft x-ray photons (3-900 eV) and their subsequent evolution with temperatures between 20 and 150 K have been investigated by near-edge x-ray absorption fine structure spectroscopy (NEXAFS) at the oxygen K edge. We observe the hydroxyl OH, the atomic oxygen O, and the hydroperoxyl HO(2) radicals, as well as the oxygen O(2) and hydrogen peroxide H(2)O(2) molecules in irradiated porous amorphous solid water (p-ASW) and crystalline (I(cryst)) ice films. The evolution of their concentrations with the temperature indicates that HO(2), O(2), and H(2)O(2) result from a simple step reaction fuelled by OH, where O(2) is a product of HO(2) and HO(2) a product of H(2)O(2).

Adsorption of HCl on the water ice surface studied by X-ray absorption spectroscopy.

The adsorption state of HCl at 20 and 90 K on crystalline water ice films deposited under ultrahigh vacuum at 150 K has been studied by X-ray absorption spectroscopy at the O1s K-edge and Cl2p L-edge. We show that HCl dissociates at temperatures as low as 20 K, in agreement with the prediction of a spontaneous ionization of HCl on ice. Comparison between the rate of saturation of the "dangling" hydrogen bonds and the chlorine uptake indicates that hydrogen bonding of HCl with the surface native water "dangling" groups only accounts for a small part of the ionization events (20% at 90 K).

[The fetal head: from screening to diagnosis].

The implementation of a prenatal screening ultrasound program to the general population requires a few rules. The sonographers must be adequately trained and the required imaging planes of the fetal head must be easy to acquire and be readily reproducible irrespective of the technology used. Screening for the presence of a potential local or global anomaly can be mainly established from a reference image.