Das Ultrarotspektrum von isotaktischem Polypropylen zwischen 1500 cm−1 und 330 cm−1

Zusammenfassung Die Frequenzen der Skelettschwingungen von isotaktischem Polypropylen werden mit Hilfe des Valenzkraft-Modells berechnet und mit den im UR-Spektrum gemessenen Frequenzen verglichen. Die übereinstimmung ist so gut, da? eine Zuordnung der Banden zu den Molekelschwingungen gegeben werden kann. Dagegen k?nnen die Intensit?tsverh?ltnisse nicht gekl?rt werden. Herrn Professor Dr.Hellwege danke ich für Anregungen und Diskussionen zu dieser Arbeit. Ferner danke ich den Firmen Kalle, Wiesbaden, und Farbwerke Hoechst für die zur Verfügung gestellten Polypropylenproben, der Deutschen Forschungsgemeinschaft für die Bereitstellung des Rechenautomaten und HerrnG. Günther für die Hilfe beim Programmieren.     

From Bq cm−3 to Bq cm−2 (and conversely)—part 2: useful dataset to apply the conversion to decommissioning operations

Journal of Radioanalytical and Nuclear Chemistry - A large set of key parameters is provided to use in decommissioning operations, the conversion method fully described in the companion paper...     

Low-frequency (20–400 cm−1) vibrational spectra of N-methylacetamide in the liquid state

Low-frequency Raman spectra (20–400 cm⁻¹) of liquid N-methylacetamide were studied. The experimental data were directly transformed into the R(v) representation. This spectrum was compared with the far infrared spectrum. Temperatures from 30 to 165 °C were investigated. A low-frequency band around 100 cm⁻¹ is assigned to a mode involving atoms in intermolecular hydrogen bonds. This assignment is qualitatively supported by the observed spectrum of Nd-methylacetamide.     

An In-Situ Cyanidation Strategy To Access Tetracyanodiacenaphthoanthracene Diimides with High Electron Mobilities Exceeding 10 cm2 V−1 s−1

A family of novel highly π-extended tetracyano-substituted acene diimides, named as tetracyanodiacenaphthoanthracene diimides (TCDADIs), have been synthesized using a facile four-fold Knoevenagel condensation strategy. Unlike conventional cyano substitution reactions, our approach enables access to a large π-conjugated backbone with the in-situ formation of four cyano substitutents at room temperature while avoiding extra cyano-functionalization reactions. TCDADIs decorated with different N-alkyl substituents present good solubility, near-coplanar backbones, good crystallinity, and low-lying lowest unoccupied molecular orbital energies of −4.33 eV, all of which contribute to desirable electron-transport performance when applied in organic field-effect transistors (OFET). The highest electron mobility of an OFET based on a 2-hexyldecyl-substituted TCDADI single crystal reaches 12.6 cm² V⁻¹ s⁻¹, which is not only among the highest values for the reported n-type organic semiconductor materials (OSMs) but also exceeds that of most n-type OSMs decorated with imide units.     

Zur Kenntnis der Salpetersäure. X Methoden zur Gasanalyse im System N2−NO−NO2−N2O4−N2O3−HNO2−HNO3

Zusammenfassung Es werden vier Methoden zur Analyse einer Gasmischung N₂–NO–NO₂–N₂O₄–N₂O₃–HNO₂ besprochen und ihre Bedeutung für die Bestimmung der einzelnen Molekelarten kritisch auseinandergesetzt. Nach keiner der Methoden kann man den Gehalt an Salpetriger Säure und Salpetersäure neben den Oxyden des Stickstoffes auffinden. Aus diesem Grunde ist die Analyse der genannten Gasmischung nach den vier Methoden allgemein nicht genau durchführbar.Mit 1 Abbildung.Herrn Prof. Dr.A. Skrabal zum 75. Geburtstag gewidmet.     

Untersuchungen in den Systemen GeO2−Na2O, −K2O und −Rb2O

Zusammenfassung Die Systeme GeO₂–Na₂O, –K₂O und –Rb₂O werden röntgenographisch und differentialthermoanalytisch untersucht. Die früher beschriebene Verbindung Na₂Ge₄O₉ (I) erweist sich als identisch mit dem vonJ. F. White und Mitarbeitern angegebenen Na₄Ge₉O₂₀. Von der dargestellten isotypen Kalium-Verbindung werden die Gitterkonstanten ermittelt. Im analogen Rubidium-System läßt sich ein isotypes Enneagermanat bisher nicht nachweisen. Einkristallaufnahmen von Natriumtetragermanat [Na₂Ge₄O₉ (II)] ergeben eine hexagonale Elementarzelle mit 6 Formeleinheiten Na₂Ge₄O₉. Ebenso werden von den isotypen Kalium-und Rubidiumtetragermanaten die Gitterparameter bestimmt. Im Natrium-System stellt offensichtlich das Enneagermanat die stabile Phase dar, während das Tetragermanat nur durch rasches Abkühlen aus der Schmelze erhalten wird. Bei den Kaliumgermanaten ist dagegen das Tetragermanat die stabile Phase.Mit 2 Abbildungen     

Low wavenumber Raman bands (300−50 cm−1) and isotopic effects of lithium acetate dihydrate

The Raman spectra in the 300−50 cm⁻¹ region were investigated for eight isotopically substituted lithium acetate dihydrates. ″LiCX₃′CO₂…2X₂″O. The observed spectral data are discussed taking the isotopic effects on the fundamental modes of vibration into consideration.     

Wavenumber shift of more than 20 cm−1 on CO vibration spectrum caused by conformational difference on polymorph in 2-cyano-3-(3,4-methylenedioxyphenyl)-2-propenoic acid

X-ray analysis of two polymorphs of 2-cyano-3-(3,4-methylenedioxyphenyl)-2-propenoic acid ethyl-ester revealed the difference of cis—trans conformation of cyano group to carbonyl group through the fixed single bond. This difference affected the carbonyl group to the extent of 20 cm⁻¹ shift in vibration and Raman spectrum.     

Magnetic properties of TlFe2−xSe2

Mössbauer studies on a mosaic of single crystals of the layered compound TlFe_2−xSe₂ have been carried out at various temperatures between 100 and 460 K. A magnetic transition occurs at ∼450 K. The magnetic ordering within the FeSe layers is antiferromagnetic with the spins oriented along the tetragonal axis. X-Ray diffraction data indicated ordering of the iron vacancies at the chosen composition (x ∼ 0.3) yielding a supercell with a volume five times that of the ThCr₂Si₂ type subcell, the cell parameters being a = 8.6909(5) Å and c = 14.005(1) Å.     

The Raman spectrum of ethane from 600 to 6500 cm−1 stokes shifts

The vibrational Raman Stokes spectrum of ethan (C₂H₆) has been recorded from 600 to 6500 cm⁻¹ using the powerful focused radiation of a free running Ar-ion laser. Measurements in bulk and in jet were performed in an intracavity arrangement. The present analysis is concentrated on totally, symmetric transitions. Numerous Q branches of overtones and binary combination tones appeared in the spectrum. All first overtones of both the degenerate and non-degenerate modes have been observed. Several multiple combination tones have also been identified. Some hot bands due to transitions starting from the thermally excited v₄ torsional level appeared as satellite Q branches. From the measured band origins the anharmonic shifts are determined and a table with the anharmonicity constants is constructed. The occurrence of a few very strong Fermi resonances enhancing the intensity of otherwise weak bands has been observed. A comparative study of some overtone Raman spectra of three substituted ethanes (CH₃CF₃, CH₃, CH₃SiH₃, CH₃CD₃) has been undertaken. The existence of a strong interaction between the CH₃ symmetric stretching modes and the overtones of the asymmetric deformation modes appears to be characteristic only for the CH₃CH₃ and CH₃CD₃ molecules.     

Intercalated hybrid of kaolinite with KH2PO4 showing high ionic conductivity (∼10−4 S cm−1) at room temperature

In this paper, we present the study of preparation and ionic conductance for an intercalated hybrid of kaolinite with potassium dihydrogen. The intercalation efficiency is high up to ca. 90%. The intercalated hybrid has been characterized by powder X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis. The ionic conductivity (σ) of the hybrid material is strongly dependent on the moisture in the environment, with σ = 8.4 × 10⁻¹⁰ S cm⁻¹ at 293 K and gradually increases to 7.16 × 10⁻⁹ S cm⁻¹ under N₂ atmosphere (anhydrous environment) at 353 K as well as an activation energy of E_a = 0.618 e V, whereas σ = 2.19 × 10⁻⁴ S cm⁻¹ at 100% relative humidity and 293 K with E_a = 0.44 eV. The mechanism that the moisture affects the ionic conductance of the intercalated hybrid is further discussed.     

Thermochemical investigations of the systems KCl−KBr−H2O,K2SO4−(NH4)2SO4−H2O and KNO3−NH4NO3−H2O at 298.15 K

For the equilibrium solid phases occurring in the systems: KCl?KBr?H₂O, K₂SO₄?(NH₄)₂SO₄?H₂O and KNO₃?NH₄NO₃?H₂O, the concentration dependencies of differential solution enthalpies, Δ_sol H ₂ for several crystallization paths, were measured. The limiting differential solution enthalpies, Δ_sol H ₂ ⁰ , were determined by extrapolation of the above dependencies to the ionic strength,I _m ⁰ , corresponding to the appropriate binary solutions. For KCl?KBr?H₂O system only, the clear dependence between Δ_sol H ₂ ⁰ andI _m ⁰ values was found and discussed.     

Preparation and properties of the systems Co1−xRhxS2, Co1−xRuxS2, and Rh1−xRuxS2

Members of the systems Co_1−xRh_xS₂ (0 ≤ x ≤ 0.6) were prepared, and their crystallographic and magnetic properties studied. The observed ferromagnetic moments for compositions where x ≤ 0.2 indicate a ferromagnetic alignment between Co(3d⁷) and Rh(4d⁷) electrons. This is the first observation of localized behavior of 4d electrons in the pyrite structure. Members of the systems Co_1−xRu_xS₂ (0 ≤ x ≤ 1) and Rh_1−xRu_xS₂ (0.5 ≤ x ≤ 1) were also prepared and their crystallographic and magnetic properties studied. From comparison with the Co_1−xRh_xS₂ system, it appears that the 4d electrons of Rh(4d⁷) are localized in the presence of Co(3d⁷) but are delocalized in the presence of Ru(4d⁶). The magnetic susceptibility of the Co_1−xRu_xS₂ system is sensitive to the homogeneity of the products and indicates that Ru(4d⁶) behaves as a diamagnetic ion.     

Formation of SO−2, SO2·O− and SO2·SO− by electron attachment to van der waals SO2 clusters

SO⁻₂, SO₂·O⁻ and SO₂·SO⁻ are produced by electron attachment to SO₂ clusters under single collision conditions. SO⁻₂, which is not produced at all in low-pressure ion sources, is more abundant than SO₂·O⁻ and SO₂ ·SO⁻. Measured relative attachment cross sections for these ions show significant differences when compared to O⁻ and SO⁻ produced by attachment to SO₂, i.e. the first resonance is very efficiently quenched in favor of SO⁻₂ production. This is in contrast to previous findings in O₂, CO₂ and N₂O.     

The Cl−NH3, Cl−H2O,F−NH3 and F−H2O clusters and their photoelectron spectra

The geometries of the Cl^–NH₃, Cl^–H₂O, F^–NH₃ and F^–H₂O clusters are optimized using the coupled cluster method. The four lowest ionization potentials are then calculated, leading to the ground and low excited states of the neutral species. The first three IPs describe ionization from the externalp state of the halogen atom, whereas the fourth corresponds to ionization from the NH₃ or H₂O moiety, leading to charge transfer complexes. These complexes were recently observed in the photoelectron spectrum of Cl^–NH₃, in full accord with our calculations.Supported in part by the U.S.-Israel Binational Science Foundation     

Conduction mechanism in Y3−2xCa2xFe5−xVxO12 garnet ferrites

A series of polycrystalline garnet ferrites with composition Y_3−2xCa_2xFe_5−xV_xO₁₂ (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), were prepared by the standard ceramic technique to study the effect of Ca²⁺ and V⁵⁺ ions substitution on their DC electrical conductivity, thermoelectric power, charge carrier concentration and charge carrier mobility at different temperatures. It was found that the DC electrical conductivity increases linearly with increasing temperature ensuring the semiconducting nature of samples. The lines representing the temperature dependence of σ_dc are broken at two-phase transition temperature (T_σ1, T_σ2=T_C) giving three distinct regions (I, II and III). The activation energy for electrical conduction increases going from ferrimagnetic state (regions I and II) to paramagnetic state (region III) through the transition temperature T_σ2 (Curie temperature). It also increases going from region I to region II thorough the temperature T_σ1. The dc electrical conductivity does not vary uniformly with Ca²⁺ and V⁵⁺ ion substitution. The values of the thermoelectric power were positive for samples of 0.0⩽x⩽0.6 indicating that the majority of the carrier are holes in these samples while it were negative for samples of x⩾0.8 indicating that the majority of charge carriers are electrons in this samples. Using the values of the DC electrical conductivity and thermoelectric power, the values of the charge carrier concentration and the charge carrier mobility were calculated.     

Light-induced FTIR difference spectroscopy of photosynthetic charge separation between 9000 and 250 cm−1

The light-induced FTIR difference spectrum corresponding to photosynthetic charge separation between the dimeric bacteriochlorophyll primary donor (P) and the quinone Q_A in the reaction center of the photosynthetic bacterium Rhodobacter sphaeroides has been measured in the frequency range between 9000 and 250 cm⁻¹ using a DTGS detector. Upon extensive signal averaging, the noise level is reduced below 2×10⁻⁵ absorbance unit. The positive bands of the difference spectrum contribute much more than the negative ones over the whole frequency range investigated. In the region below 650 cm⁻¹, a number of bands of small amplitude are observed for the first time. The presence of a tail extending between 6000 and 3600 cm⁻¹ on the high-energy side of the electronic transition of P⁺ peaking at ≈2600 cm⁻¹ [J. Breton, E. Nabedryk, W.W. Parson, Biochemistry, 31 (1992) 7503–7510] is confirmed.