A model of structures of monolayers adsorbed on (100) faces of metals: A comparative study of various systems in the high symmetry coincidence mesh hypothesis

Recently, Huber and Oudar, have proposed a model for the structure of certain adsorbed layers. They have shown that an interpretation of LEED patterns based on the high symmetry of the coincidence mesh and a minimum number of different kinds of adsorption site gives rise to a structure of the adsorbate in rows or polygons. We propose here the application of the same model in the case of adsorption of a metal on (100) faces of cubic metals. We show that without knowing accurately the concentrations, but only the succession of the patterns, it is possible to deduce a model for the adsorbed layer. We give a classification of the different structures.     

Riemannsche Flächen von hyperbolischem Typus im euklidischen Raum

Ohne Zusammenfassung     

Dyads containing iridium(III) bis-terpyridine as photoactive center: synthesis and electron transfer study

A series of Ir(III)-D dyads based on an iridium(III) bis-terpyridine complex as a photoactive center and tertiary amines as donor groups, as well as their individual components, have been designed to generate photoinduced charge separation. Depending on the donor group, a modular approach or a "chemistry-on-the-complex" approach has been used to prepare three different Ir(III)-D dyads. A detailed photophysical study has been performed on one Ir(III)-D dyad in which a triarylamine is linked to the iridium bis-terpyridine complex with an amido-phenyl group used as a spacer. In acetonitrile at room temperature, steady-state and time-resolved methods gave evidence of a photoinduced charge-separated state Ir(-)-D(+) with a lifetime of 70 ps. This relatively short lifetime could be due to the close proximity between the negative charge, likely localized in the bridging terpyridine, and the oxidized donor group.     

Oxygenation of thiolates to S-bonded sulfinate in an iron III complex related to nitrile hydratase

Air oxidation of the iron(III) complex derived from (2-mercaptoisobutyryl)-4,5-dichloro-O-phenylenediamine in the presence of Et4NCN afforded the corresponding disulfinato species. With two carboxamido nitrogens trans to two S-bonded sulfinates, this complex mimics the disulfinate inactive form of Fe-NHase.     

Photochemical behavior of a new long-chain UV absorber derived from 4-tert-butyl-4'-methoxydibenzoylmethane

A new UV filter, the 1-(4-tert-butylphenyl)-2-decanyl-3-(4'-methoxyphenyl)-propane-1,3-dione, called C10-DBM, was prepared by grafting a 10-carbon aliphatic chain to the alpha-carbonyl position of 4-tert-butyl-4'-methoxydibenzoylmethane (BM-DBM), a well-known and often used UV filter. The UV-A absorption efficiency of organic solutions containing the new filter was tested and compared with identical solutions containing BM-DBM with or without irradiation (xenon lamp). The originality of this new filter is that its UV-A absorbance appeared during irradiation of the molecule. Although the molar absorption coefficient of C10-DBM in the UV-A domain was lower than that of BM-DBM, the solutions absorption exhibited a much more photostable behavior under irradiation. In this study, we first demonstrated that C10-DBM was a precursor of BM-DBM (enol isomer) by means of high-performance liquid chromatography followed by mass spectrometry. Indeed, we showed that the UV-A absorption of C10-DBM solutions appearing during the irradiation of the molecule was due to a Norrish-II reaction (beta-cleavage), which induced the release of the BM-DBM enol form and 1-decene. Then, we established a kinetic model for the photochemistry of C10-DBM and fitted the variation of UV absorption spectra to confirm the proposed mechanism.     

1.9- m and 2.0- m laser diode pumping of Cr(2+) :ZnSe and Cr(2+) :CdMnTe

Efficient diode pumping at wavelengths of 1.9 and 2.0microm of a Cr(2+): ZnSe laser with an output power of 105 mW and a slope efficiency of 35% with respect to the absorbed pump power is presented. In addition, Cr(2+): CdMnTe has been laser diode pumped as well as operated in the continuous-wave regime, to the best of our knowledge for the first time.     

Diode-pumped continuous-wave green upconversion lasing of Er(3+):LiLuF(4) using multipass pumping

Powerful green upconversion lasing of Er(3+):LiLuF(4) was achieved with a multipass pumping setup. The maximum output was 213 mW for Ti:sapphire laser pumping. Diode-pumped cw lasing at room temperature is demonstrated for the first time to the authors' knowledge.