Tris­[(R)‐lact­amide‐κ2O,O′]­zinc(II) tetra­bromo­zincate

The title compound, tris­[(R)‐2‐hydroxy­propan­amide‐κ²O,O′]­zinc(II) tetra­bromo­zincate, [Zn(C₃H₇NO₂)₃][ZnBr₄], contains one monomeric six‐coordinate zinc complex cation and one tetrahedral [ZnBr₄]²⁻ anion. Both Zn^II atoms lie on threefold axes. Coordination in the cation occurs via the amide and hydroxy O atoms [Zn—O = 2.074 (5) and 2.073 (6) Å] and has a distorted octahedral geometry, with cis‐O—Zn—O angles in the range 76.2 (2)–109.2 (2)°. In the crystal structure, the cations and anions are linked by N—H⋯Br and O—H⋯O hydrogen bonds, generating a three‐dimensional network.     

Infrared HCN Lineshapes as a Test of Galatry and Speed-Dependent Voigt Profiles

Absorption lineshapes of the ν₂ infrared band of HCN in collision with He, Ne, Ar, Kr, Xe, N₂, HCN, and CH₃Br have been considered. Observed lineshapes differ significantly from the usual Voigt profile and are characteristic of line narrowing processes. The Galatry profile fairly reproduces lineshapes observed in the low-pressure regime, but leads to unexpected nonlinear behavior of optical diffusion rates in the high-pressure regime and strongly fails with the heaviest perturbers. On the other hand, fair results are obtained for all experimental conditions by using a speed-dependent Voigt profile that includes a pressure-dependent narrowing parameter. These observations are discussed by consideration of the polarization correlation functions related to considered line profiles and of the optical and kinetic radii involved in collision processes. It is shown that observed line narrowings primarily result from the dependence of relaxation rates on molecular speeds and that diffusion processes show up with the two lighter perturbers only, He and, to a small extent, Ne. Finally, it can be claimed that, for atmospheric applications, deviations from the Voigt profile must be taken into account by a speed-dependent Galatry profile that reduces to a speed-dependent Voigt profile in most cases.     

Resazurin

Ohne Zusammenfassung     

Ueber die Wirkung des Magnesiums auf Salzl?sungen

Ohne Zusammenfassung     

Evaluation of temperature gradients within combusting droplets in linear stream using two colors laser-induced fluorescence

The scope of this paper concerns the heating process of fuel droplets injected in a hot gaseous environment. The two colors laser-induced fluorescence technique allows measuring the temperature distribution within a droplet by scanning the droplet volume by a sufficiently small probe volume compared to the droplet volume itself. The temperature field is reconstructed using two approaches which have been compared. One is based on a geometrical optics model and the other is based on the 3D calculation of the internal excitation field within the droplet, using the generalized Lorenz-Mie theory. Experimental results have been obtained on a combusting monodisperse ethanol droplet stream (diameter around 200 m).     

Carbon nanostructures grown with electron and ion beam methods

We present a comparative study where carbon nanostructures were prepared by electron and ion beam methods. Thin films of 10×10 μm² area were prepared and analysed by Raman analysis, nanoindentation, energy dispersive X-ray analysis (EDX) and atomic force microscopy (AFM). The material formed is not soft and graphitic, but of intermediate hardness (6–13 GPa) and with Raman spectral features similar to those of hydrogenated amorphous carbon, although it contains a significant Ga content (up to 25 at. %). This study was used to form sharp AFM supertip structures which were used to image sintered ceramic samples and films of aligned carbon nanotubes. Compared to traditional Si tips, this gave an improved rendering of the sample’s aspect ratio although the resolution is limited by the diameter of the C supertips. PACS 81.05.Uw; 81.07.-b; 78.30.-j     

Intrinsic mechanical properties of ultra-thin amorphous carbon layers

In this work, we extracted the film's hardness (H_F) of ultra-thin diamond-like carbon layers by simultaneously taking into account the tip blunting and the substrate effect. As compared to previous approaches, which did not consider tip blunting, this resulted in marked differences (30-100%) for the H_F value of the thinner carbon coatings. We find that the nature of the substrate influences this intrinsic film parameter and hence the growth mechanisms. Moreover, the H_F values generally increase with film thickness. The 10 nm and 50 nm thick hydrogenated amorphous carbon (a-C:H) films deposited onto Si have H_F values of, respectively, ∼26 GPa and ∼31 GPa whereas the 10 nm and 50 nm thick tetrahedral amorphous carbon (t-aC) films deposited onto Si have H_F values of, respectively, ∼29 GPa and ∼38 GPa. Both the a-C:H and t-aC materials also show higher density and refractive index values for the thicker coatings, as measured, respectively by X-ray reflectometry and optical profilometry analysis. However, the Raman analysis of the a-C:H samples show bonding characteristics which are independent of the film thickness. This indicates that in these ultra-thin hydrogenated carbon films, the arrangement of sp² clusters does not relate directly to the hardness of the film.