Abstract: The quartic force field of thioformaldehyde has been calculated ab initio using large basis sets and augmented coupled cluster methods. Calculated fundamentals are in excellent agreement with experiment, as is the most important Coriolis coupling constant. Computed values for the anharmonicity, rovibrational coupling, and centrifugal distortion constants of the four isotopomers (H2CS)-S-32, (H2CS)-S-34, (HDCS)-S-32, and (D2CS)-S-32 have been reported. Predictions have been made for all vibrational transitions from the ground state to excited states with at most two quanta for these isotopomers, both using second-order perturbation theory corrected for Darling-Dennison resonance and using vibrational SCF-CI calculations. For (D2CS)-S-32, perturbation theory performs quite well; for the other isotopomers, performance is poorer for states involving excitation of the out-of-plane bend and, for the (H2CS)-S-32 and (H2CS)-S-34 isotopomers, also for the antisymmetric bend that is in severe Coriolis resonance with it. A possible explanation has been suggested. (C) 1994 Academic Press, Inc.

Abstract: In this work self-supporting tin dioxide disks are characterized using FT-IR spectroscopy in the presence of a reducing gas in air, and in different O2/N2 mixtures at temperatures varying from room temperature up to 450°C. Every factor inducing a change in the oxygen content of the gas atmosphere above the tin dioxide, as for instance a temperature change, a surface reaction or adsorption of another species, induces a broad, intense IR absorption band with discrete weak bands superimposed on it. This broad absorption is assigned to the electronic transition from a native donor level, the oxygen vacancy in the bulk of the domain, to the conduction band of the tin dioxide material. For the interpretation of the narrow, superimposed absorptions, two hypotheses remain. The results demonstrate that FT-IR spectroscopy is an extremely suitable technique for the characterization of semiconducting metal oxide sensors, since it allows to follow in situ the processes in the bulk, at the surface and in the surrounding gas atmosphere of the sensor material at working temperature as well as in the presence of reducing gases in air.

Abstract: Twenty-seven glass fragments containing dark coloured grisaille paint layers of different qualities were collected from ten windows of the cathedral St. Michael & St. Gudule in Brussels (Belgium). The windows were made by J.-B. Capronnier (18141891) and cover the period between 1843 and 1878. The samples were cross-sectioned and examined in an electron microscope. Grisaille paint layers are not homogeneous and therefore, it is not meaningful to characterize them in terms of their average composition. Instead, parameters such as granularity, the number of residual gas bubbles per running millimetre of paint, the type of pigments, and the thickness of the paint layer were used to characterize them. The microscopic morphology allows a classification of the grisaille paint layers in four groups, every group associated with a quality level. Moreover, the main causes of the accelerated degradation of some of these paint layers could be explained. The classification made it possible to distinguish two periods in the work of Capronnier: (1) the early period (18431848) is characterized by the presence of either single granular paint layers or of double-layered systems consisting of a granular paint layer on top of a well-melted paint layer. The granular grisaille paint layers tend to pulverize; (2) the later period (18481878) is characterized by the presence of only well-vitrified paint layers. No sign of deterioration was found on the well-vitrified paint layers.