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K.H. Schmidt

Bio: K.H. Schmidt is an academic researcher from Technical University of Dortmund. The author has contributed to research in topics: Raman spectroscopy & Infrared spectroscopy. The author has an hindex of 13, co-authored 25 publications receiving 447 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the vibrational spectra of [ 50 Cr(NH 3 ) 6 ] 3+, [ 53 Cr(Ni 3 ) 4 ] 2+, and [ 110 Pd(Ni 4 ) 4 ) 2+ have been recorded and the measured isotope shifts could be used to solve some assignment problems.

36 citations

Journal ArticleDOI
TL;DR: In this article, the i.r. and Raman spectra of the following compounds have been measured: Tl 3 VS 4, Tl3 NbS 4,Tl 3 TaS 4, Tl 2 VSe 4, tl 3 NbSe 4 and Tl 1 TaSe 4 with other cations are given.

28 citations

Journal ArticleDOI
TL;DR: In this paper, the fundamental vibrational frequencies and some overtone and combination bands of H13CCl3 have been determined from high-resolution infrared absorption studies in the gaseous phase.

24 citations


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Journal ArticleDOI
TL;DR: In this article, the sulfidation of crystalline MoO3 and the thermal decomposition of (NH4)2MoO2S2 to MoS2 via an {MoOS2} oxysulfide intermediate have been studied by means of monochromatic X-ray photoelectron spectroscopy (XPS) and IRES.
Abstract: The sulfidation of crystalline MoO3 and the thermal decomposition of (NH4)2MoO2S2 to MoS2 via an {MoOS2} oxysulfide intermediate have been studied by means of monochromatic X-ray photoelectron spectroscopy (XPS) and infrared emission spectroscopy (IRES) Several basic steps of the sulfidation reaction could be resolved and explained in terms of the structure of crystalline MoO3 The sulfidation reaction starts at low temperatures with an exchange of terminal O2- ligands of the oxide for S2- by reaction with H2S from the sulfiding atmosphere In subsequent Mo−S redox reactions, bridging S22- ligands and Mo5+ centers are formed Lattice relaxation and further sulfur uptake are the main processes before, at temperatures above 200 °C, direct reactions with H2 occur, during which the Mo5+ centers are converted into the 4+ oxidation state The decomposition experiments with (NH4)2MoO2S2 show that terminal O2- ligands serve as the reactive sites The conversion of terminal MoOt to MoS entities and the subsequent

418 citations

Journal ArticleDOI
TL;DR: In this article, the molecular and electronic structures of the dehydrated supported metal oxides and the SiO2 support were determined by combined in situ Raman, IR, and UV−vis spectroscopy under dehydrated conditions.
Abstract: Groups 5−7 transition metal oxides (V2O5, Nb2O5, Ta2O5, CrO3, MoO3, WO3, Re2O7) were anchored on a SiO2 support via incipient wetness impregnation and calcination. The molecular and electronic structures of the dehydrated supported metal oxides and the SiO2 support were determined by combined in situ Raman, IR, and UV−vis spectroscopy under dehydrated conditions. In situ Raman characterization reveals that the supported metal oxides are only present as surface species below the maximum dispersion limit (where crystalline metal oxide nanoparticles are absent). In situ IR analysis shows that the surface metal oxides anchor to the SiO2 support at Si−OH and adjacent Si−O−Si sites. The corresponding in situ UV−vis diffuse reflectance spectroscopy indicates that the dehydrated surface metal oxide species are present as isolated structures. Isotopic D2O−H2O exchange demonstrates that the dehydrated surface MOx species possess the MO oxo functionality but no MOH bonds. The number of MO oxo bonds was found to be r...

282 citations

Journal ArticleDOI
29 Jun 2018-Science
TL;DR: This work identifies a simple crystal, Tl3VSe4, with a calculated phonon κ one-half that of the measured κ, and suggests that a two-channel model is necessary for crystals with ultralow κ.
Abstract: Solids with ultralow thermal conductivity are of great interest as thermal barrier coatings for insulation or thermoelectrics for energy conversion. However, the theoretical limits of lattice thermal conductivity (κ) are unclear. In typical crystals a phonon picture is valid, whereas lowest κ values occur in highly disordered materials where this picture fails and heat is supposedly carried by random walk among uncorrelated oscillators. Here we identify a simple crystal, Tl 3 VSe 4 , with a calculated phonon κ [0.16 Watts per meter-Kelvin (W/m-K)] one-half that of our measured κ (0.30 W/m-K) at 300 K, approaching disorder κ values, although Raman spectra, specific heat, and temperature dependence of κ reveal typical phonon characteristics. Adding a transport component based on uncorrelated oscillators explains the measured κ and suggests that a two-channel model is necessary for crystals with ultralow κ.

194 citations