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.     

Origin of the doublet at 1360 and 1340 cm−1 in the Raman spectra of tryptophan and related compounds

Raman spectra of indole, skatole, tryptophan and its derivatives including C₄-monodeuterated tryptophan were studied with special attention to the origin of the band around 1350 cm⁻¹. The band is observed as a doublet or triplet depending on the compound and solvent, which was ascribed to Fermi resonance between one fundamental and one or two combination bands of the out-of-plane bending vibrations. Removal of the interaction is seen for C₄D-tryptophan and some solutions of skatole. The assignments of the component vibrations were made based on the shifts in frequencies upon C₄-deuteration. In tryptophan derivatives the doublet (or triplet) peaks exhibit steep changes in relative intensity at the pK_a points of the dissociable groups, which is ascribed as arising from slight frequency shifts of a pK_a-sensitive component vibration. Relations between the relative intensity and environment of indole were obtained and their possible applicability to the analyses of Raman spectra of proteins is suggested.     

ATR-FT-IR spectral collection of conservation materials in the extended region of 4000-80 cm–1

In this paper, a spectral collection of over 150 ATR-FT-IR spectra of materials related to cultural heritage and conservation science has been presented that have been measured in the extended region of 4000-80 cm^–1 (mid-IR and far-IR region). The applicability of the spectra and, in particular, the extended spectral range, for investigation of art-related materials is demonstrated on a case study. This collection of ATRFT-IR reference spectra is freely available online (http://tera.chem.ut.ee/IR_spectra/) and is meant to be a useful tool for researchers in the field of conservation and materials science.     

Ozonization of sodium hydroxide in the temperature range from −100 tO +50°

Summary The process of ozonization of sodium hydroxide was studied in the temperature interval from –100 to +50°. The time and temperature dependences of the yield of sodium ozonide were obtained.     

Crystal chemical and dielectric investigation of the system LiZnV1−xPxO4

An X-ray crystallographic study has allowed us to identify a solid solution of the type LiZnV_1−xP_xO₄ (0≤ x ≤0.6) inside the binary system LiZnVO₄-LiZnPO₄. The structure is isotypic with the phenacite like LiZnVO₄. X-ray diffraction patterns are indexed according to the lattice parameters of the trigonal system and the space group R3. The mother structure can be regarded as made of a three-dimensional network of LiO₄, ZnO₄ and VO₄ tetrahedra all having one apex oriented along [001]. The peaks, observed on the curves of the thermal variation of the dielectric constants, have allowed us to recognize a phase transition whose temperature varies continuously along the solid solution.     

Spectroscopy of H 3 + with energies above the barrier to linearity: rovibrational transitions in the range of 10,000–14,000 cm−1

Based on a recently extended potential energy surface for H ₃ ⁺ with a highly reliable form of the topology of the surface far beyond the barrier to linearity, rovibrational frequencies in the range of 10,000–14,000 cm^?1 have been derived and are compared with new experiments. The computed transition frequencies reproduce experimental transitions mostly within a few tenths of a wavenumber, if non-adiabatic effects are crudely simulated using different reduced masses for vibrational and rotational motions. Deviations can only be compensated if non-adiabatic effects are treated more rigorously.     

Infrared spectra of triacetylene in the 4000-220 cm−1 region: Absolute band intensity and implications for the atmosphere of Titan

The gas phase infrared spectra of triacetylene were studied at room temperature in the 4000-220 cm⁻¹ wavenumber region. The absolute intensity of all the bands of noticeable strength were experimentally determined and the associated uncertainties were systematically estimated. The data obtained were then used for studying the detectability of C₆H₂ in Titan's atmosphere by means of infrared spectroscopy. The upper limit of mean stratospheric abundance derived from the already available Titan IR spectra (a fraction of ppb) is in agreement with the photochemical model estimates.     

Comparative investigation of LiNbO3 crystals Raman spectra in the temperature range 100–400 K

We have investigated Raman spectra of congruent and stoichiometric LiNbO₃ crystals in the temperature range 100–450 K. Slope gradient is greater for the temperature dependence of band width associated with Nb⁵⁺ ions vibrations than that associated with Li⁺ ions vibrations in a lithium niobate crystal structure. This fact indicates that the anharmonicity of Nb⁵⁺ ions vibrations along the polar axis is greater compared to Li⁺ ions vibrations. It is likely that O^2– ions contribute to this anharmonicity. The O^2– ions vibrations are characterized by an anharmonic potential in the LiNbO₃ crystal structure. The O^2– ions vibrations according to ab initio calculations strongly interact with vibrations of Nb⁵⁺ ions. We have found that the temperature dependence of the fundamental bands intensity is nonmonotonic and the “extra bands” intensity is strictly linear.     

Effect of pH and α-, β- and γ-cyclodextrin on the spectral properties of etoricoxib: spectroscopic and molecular dynamics study

The spectral properties of etoricoxib (ETR) at pH 2.0, 6.0 and 10.0 in the presence of cyclodextrins (CDs) were investigated. The absorption spectrum of ETR in acidic medium exhibited two bands centered at 236 and 273 nm, while in basic medium it exhibited two bands centered at 236 and 285 nm. No change in the spectrum was observed in the presence of CDs. The fluorescence emission spectra of ETR in acidic and basic media exhibited one band at 380 nm and another one at 484 nm. The emission band at 484 nm was enhanced when ETR was complexed with β-CD and γ-CD at pH 2.0, 6.0 and 10.0, while the band at 380 nm was enhanced selectively when ETR was complexed with α-CD at pH 2.0. Molecular dynamics simulations computations revealed that at pH 2.0, the sulfonyl moiety of H₂ETR²⁺ is preferentially included within the α-CD cavity, which is believed to cause the enhancement of the band at 380 nm. Moreover, at pH 6.0 and 10.0, the enhancement of the band at 484 nm was related to the inclusion of the chloropyridinyl and methylpyridinyl groups of the bipyridine moiety of HETR⁺ and ETR within β-CD and γ-CD cavities. Benesi–Hildebrand analysis showed that the ETR/β-CD complex adopts a 1:1 stoichiometry with association constant of K ₁₁?=?64.8 at pH 2.0, K ₁₁?=?105.4 at pH 6.0 and K ₁₁?=?520.5 at pH 10.0.     

Optical waveguide dosimetry for gamma-radiation in the dose range 10-1 − 104 Gy

Two types of liquid-core optical waveguide (OWG) dosimeters are commercially available for dosimetry in the irradiation of foods and other products. “Opti-chromic” type FWT-70-40M has a useful range of about 10-10⁴ Gy and type FWT-70–83M about 10²−10⁴ Gy. 5 Within the limits of random uncertainty of the reading of the absorbed dose (±5%, 1σ), the response to γ-radiation is independent of dose rate over the range 10^-1−10⁴ Gy/h, when measured at the peak of the spectrum [absorption band maximum (600 nm wavelength)]. The response curve is linear with dose up to ≈10³ Gy, but is non-linear at higher doses, where the readings are made away from the absorption peak (656nm). Both dosimeter types when measured at 600 nm are temperature dependent over the temperatures ranges of -40 to 60°C during irradiation. The dosimeters cannot be used when exposed to temperatures > 60°C because of bubble formation and loss of light propagation. At doses < 10³ Gy (at600 nm), the dosimeters are stable (in terms of dose readings) for several months following irradiation, but at doses ≈ 10⁴ kGy (at 656 nm), they show a gradual absorbance increase (error in dose interpretation), over post-irradiation storage periods longer than 1 month. A special, sensitive OWG dosimeter (50-cm coil), designed for doses down to 10^-1 Gy, shows a linear response up to at least 15 Gy, a temperature dependence of response only at temperatures below ≈ 20°C, and no dose-rate dependence.     

Temperature and Heat Flow Calibration of A DSC-instrument in the Temperature Range Between −100 and 160°C

Thermoanalytical instruments are extensively used in R&D as well as in industrial quality control. A quantitative analysis of the data of a thermoanalytical measurement requires a careful calibration of the instrument. In differential scanning calorimetry (DSC) the quantities that have to be calibrated are the temperature and the heat flow. These two quantities are usually calibrated by evaluating melting or solid-solid transitions of some reference materials with well known transition enthalpies and temperatures. In this contribution we investigate temperature and heat flow calibration in the temperature range between −100 and 160°C. We included 9 different samples for the analysis and established some general rules for the calibration process. As a result we found that with a well calibrated instrument the heat flow can be measured with 90% confidence to about ± 3% accuracy in this temperature range. With respect to temperature calibration we find that accuracies of ±0.8°C (90% confidence) may be expected. These values represent general accuracy limitations of DSC’s due to varying heat transfer conditions within the samples. This revised version was published online in July 2006 with corrections to the Cover Date.     

Infrared spectra of cyclohexane-1,3-dione derivatives in the region of 1750–1550 cm−1

Russian Chemical Bulletin -     

A full vibrational assignment (4000-50 cm−1) of 1, 10-phenanthroline and its perdeuterated analogue

Full infrared and Raman vibrational assignments (4000-50 cm⁻¹) of 1,10-phenanthroline are presented and full infrared assignments (4000-50 cm⁻¹) of 1,10-phenanthroline-d₈ are given. Four fundamentals are newly reported for 1,10-phenanthroline and several changes are recommended to earlier assignments for this compound. The assignments of the fully deuterated analogue are newly reported.     

A Mössbauer spectroscopy investigation of SrFe1−xScxO3−δ perovskites

Polycrystalline samples of oxygen deficient perovskites SrFe_1?xSc_xO_3?δ (0 ≤ x ≤ 0.5) have been synthesized by direct solid state reactions. Each compound has been stabilized with two different oxygen stoichiometries. The structural study shows, firstly, the good cationic homogeneity of the samples and, secondly, that the Sc and Fe atoms are randomly distributed over the same crystallographic site, whatever the scandium content. This implies that no anionic order is possible. A detailed Mossbauer spectroscopy study clearly shows that the substitution of scandium for iron involves an oxygen content decrease which decreases the tetravalent iron content until its total disappearance for x = 0.5. The evolutions of the isomer shift, the quadrupolar splitting and the relative intensity versus the Sc³⁺ content are depicted in the present paper.     

Analysis of the rotational structure of the 2ν9 band of HNO3 between 891 and 898 cm−1

Several lines belonging to the 2ν₉ band of nitric acid have been assigned on a spectrum recorded with a tunable diode laser around 895 cm⁻¹. This analysis has led to the determination of the band centre and six rotational constants (A, B, C, Δ_K, Δ_JK, Δ_J) for the vibrational level v₉ = 2. For the transitions involved in the calculation the overall standard deviation is 0.005 cm⁻¹.     

Synthesis,spectroscopic and thermal structural investigations of the charge-transfer complexes formed in the reaction of 1-methylpiperidine with σ- and π-acceptors

The reactions of the electron donor 1-methylpiperidine (1MP) with the π-acceptors 7,7,8,8-tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil = CHL) and iodine (I₂) were studied spectrophotometrically in chloroform at room temperature. The electronic and infrared spectra of the formed molecular charge-transfer (CT) complexes were recorded. The obtained results showed that the stoichiometries of the reactions are not fixed and depend on the nature of the acceptor. Based on the obtained data, the formed charge-transfer complexes were formulated as [(1MP)(TCNE)₂], [(1MP)(DDQ)]·H₂O, [(1MP)(CHL)] and [(1MP)I]I₃, while in the case of 1MP–TCNQ reaction, a short-lived CT complex is formed followed by rapid N-substitution by TCNQ forming the final reaction products 7,7,8-tricyano-8-piperidinylquinodimethane (TCPQDM). The five solids products were isolated and have been characterized by electronic spectra, infrared spectra, elemental analysis and thermal analysis.     

Vibrational spectroscopic study of the hypophosphite and phosphite anions,H2PO2−2 and HPO2−3, and of their deuteriated analogues in the solid state and in aqueous solution

A full vibrational spectroscopic study of sodium hypophosphite, sodium phosphite and their deuteriated analogues has been made. The vibrations characteristic of the hypophosphite anion have been assigned and the presence of a previously unreported band has been established for the Raman spectrum of the aqueous solution. The first Raman study of deuteriated sodium phosphite has been undertaken and a full vibrational assignment is given.