Ionization Potential Depression in Hot Dense Plasmas Through a Pure Classical Model

The ionization potential of an ion embedded in a plasma, lowered due to the whole of the charged particles (ions and electrons) interacting with this ion, is the so‐called plasma effect. A numerical plasma model based on classical molecular dynamics has been developed recently. It is capable to describe a neutral plasma at equilibrium involving ions of various charge states of the same atom together with electrons. This code is used here to investigate the ionization potential depression (IPD). The study of the IPD is illustrated and discussed for aluminum plasmas at mid and solid density and electron temperatures varying from 50eV to 190eV. The method relies on a sampling of the total potential energy of the electron located at an ion being ionized. The potential energy of such electron results from all of the interacting charged particles interacting with it. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystalline properties and colour centres in alkali halide thin films

Abstract

Thin films of KCl, KBr, RbCl have been obtained by thermal evaporation on amorphous substrates with different deposition parameters. The crystalline structure and orientation have been determined, and the films resulted to be policrystals with high uniformity of orientation. Production of colour centres, achieved by irradiation with low-energy electrons, leads to F center concentrations barely observed in large crystals. The colouration kinetics is similar to that in the bulk, and shows after a maximum an exponential decay at high doses because of centre aggregation coupled to thermal effects. The films exhibit a bleaching process of the colour centres at room temperature, whose kinetics depends on the irradiation damage.     

Statistical, noise-related non-classicality’s indicator

Finding signs of the classical-quantum border is a very important task of perennial interest. We show, using semiclassical arguments, that the frontier between the classical and quantum domains can be characterized by recourse to idiosyncratic features of a delimiter parameter associated with the concepts of i) noise) ii) Husimi distribution functions, iii) Wherl’s entropy, and iv) escort distributions.      

Exploring the synthetic potency of the first furanothioglycoligase through original remote activation

Thioglycosidic bonds are of utmost importance in biomolecules as their incorporation led to more stable glycomimetics with potential drug activities. Until now only chemical methods were available for their incorporation into glycofuranosyl conjugates. Herein, we wish to describe the use of the first furanothioglycoligase for the preparation of a great variety of thioaryl derivatives with moderate to excellent yields. Of great interest, a stable 1-thioimidoyl arabinofuranose, classically used in chemical glycosylation, was able to efficiently act as a donor through an original enzymatic remote activation mechanism. Study of the chemical structure as well as the nucleophilicity of the thiol allowed us to optimize this biocatalyzed process. As a consequence, this mutated enzyme constitutes an original, mild and eco-friendly method of thioligation.     

Chirally modified platinum generated by adsorption of cinchonidine ether derivatives: towards uncovering the chiral sites

The adsorption behavior of O-methyl and O-trimethylsilyl derivatives of cinchonidine (CD), employed as chiral modifiers for heterogeneous enantioselective hydrogenations on supported Pt catalysts, has been investigated by using attenuated total reflection infrared spectroscopy (ATR-IR) and density functional theory (DFT) electronic structure calculations. The ATR-IR spectroscopic investigation provided detailed insight of the adsorbed modifiers under conditions close to those employed during catalytic processes, and electronic structure calculations were used as a complement to the experiments to uncover the implications of conformational changes in generating the topology of the surface chiral site. The structural investigation of the adsorbed modifiers revealed a relationship between the spatial positions of the ether substituents and the enantiodifferentiation induced by the modified catalyst observed in the hydrogenation of alpha-activated ketones. Experiments and calculations corroborate a model, according to which the addition of a bulky ether group to CD reshapes the chiral sites, thus generating catalytic chiral surfaces with different and, in some cases (e.g. hydrogenation of ketopantolactone), even opposite enantioselective properties to those obtained with CD without altering the absolute configuration of the modifier. The study also confirms that active surface conformations of cinchona modifiers are markedly different from those existing in vacuum and in solution, thus underlying the necessity of investigating the surface-modifier interaction in order to understand enantioselectivity.     

Focusing surface plasmons on Er3+ ions through gold planar plasmonic lenses

Gold plasmonic lenses consisting of a planar concentric rings-groove with different periods were milled with a focused gallium ion beam on a gold thin film deposited onto an Er³⁺-doped tellurite glass. The plasmonic lenses were vertically illuminated with an argon ion laser highly focused by means of a 50× objective lens. The focusing mechanism of the plasmonic lenses is explained using a coherent interference model of surface plasmon-polariton (SPP) generation on the circular grating due to the incident field. As a result, phase modulation can be accomplished by the groove gap, similar to a nanoslit array with different widths. This focusing allows a high confinement of SPPs that can excite the Er³⁺ ions of the glass. The Er³⁺ luminescence spectra were measured in the far-field (500?C750?nm wavelength range), where we could verify the excitation yield via the plasmonic lens on the Er³⁺ ions. We analyze the influence of the geometrical parameters on the luminescence spectra. The variation of these parameters results in considerable changes of the luminescence spectra.     

Surface processes occurring on Rh/alumina during chiral modification by cinchonidine: an ATR-IR spectroscopy study

Cinchona alkaloids are frequently used for chiral modification of supported noble metal catalysts employed in heterogeneous enantioselective hydrogenation. In order to gain molecular insight into the surface processes occurring at the metal/liquid interface, cinchonidine (CD) adsorption on vapor-deposited Rh/Al2O3 films has been studied in the presence of solvent and hydrogen by means of attenuated total reflection infrared (ATR-IR) spectroscopy. The spectrum of CD adsorbed on Rh exhibited two dominant signals at 1593 and 1511 cm(-1), which are characteristic of a surface species having a quinoline ring tilted with respect to the metal. Interestingly, no adsorbed modifier in the flat geometry (quinoline parallel to the metal plane) was observed. During desorption, these signals vanished, and a new prominent signal appeared at 1601 cm(-1) which belongs to a species with the quinoline ring hydrogenated on the heteroaromatic side. Concentration-dependent experiments and the reversibility of the observed phenomenon indicate that CD was readily hydrogenated to 1',2',3',4',10,11-hexahydrocinchonidine (CDH(6)) on Rh. The ATR-IR spectra also reveal that the flat species was indeed immediately hydrogenated when CD was provided from solution, and the only visible adsorbed species was the tilted species, which displaced the hydrogenation product from the metal surface. In the absence of dissolved CD, during desorption, the tilted species was converted to the flat species and rapidly hydrogenated. The hydrogenation product was stable on the metal surface only in the absence of CD. Therefore, the adsorption strength of the different species is as follows: flat > tilted > CDH(6). Evidence for the formation of the flat species and its role as an intermediate to the hydrogenation product is given by an experiment in which CD was adsorbed in the absence of dissolved hydrogen after surface cleaning. The adsorption and hydrogenation of CD on Rh deviate significantly from that observed earlier on Pt and Pd under similar conditions, where the flat species could be observed even in the presence of hydrogen. This difference is attributed to the weaker interaction and lower hydrogenation rate occurring on Pt and Pd.