für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution 4.0 International License. Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namensnennung 4.0 Lizenz. 79,81 Br and 133Cs Nuclei Quadrupole Interactions and Phase Transitions in Crystalline Caesium Perbromate

The formation of hydrogen bonds and molecular dynamics of alkenylphenol derivatives has been investigated in solution using nuclear magnetic resonance. The results confirm formation of an N···H, O···H-type intramolecular hydrogen bond. The spin–lattice relaxation times ( T 1 ) and activation energy of molecular dynamics have been investigated confirming the importance of relaxation times as a very sensitive tool for studying molecular mobility.

The formation of hydrogen bonds and molecular dynamics for the molecules cis ‐1‐(2‐hydroxy‐5‐methylphenyl)ethanone oxime ( I ) and N ‐(2‐hydroxy‐4‐methylphenyl)acetamide ( II ) have been investigated in solution using NMR. The results confirm the formation of OH···O, OH···N and O···HN type inter‐ and intramolecular hydrogen bonds. Spin‐lattice relaxation times ( T 1 ), activation energy of molecular dynamics and energy of intramolecular hydrogen bonds have been determined. Copyright © 2010 John Wiley & Sons, Ltd.

The possibility of modifying boron polyoxide with an oligomeric amide upon thermal dehydration of orthoboric acid and oligomerization of caprolactam in a common melt is shown. The products obtained after thermal pretreatment of the initial blend containing 30 wt % caprolactam are investigated. It is shown that the main processes at T < 200°C are dehydration of orthoboric acid and hydrolysis of caprolactam with the formation of ε-aminocaproic acid. At temperatures of 225–260°C, the predominant process is the formation of boron polyoxide and a caprolactam-based oligomeric product. The data of 11B NMR spectroscopy show that the chemical transformations of caprolactam occur against the background of the N:B donor-acceptor interaction. The two-dimensional [11B-1H] heteronuclear correlation spectrum indicates that the systems obtained upon thermal treatment are solid solutions.

Step Scan creates an identical IR modulation frequency over the entire IR spectrum. This is a prerequisite for quantitative photoacoustic spectroscopy and depth profiling. 2D correlation maps have been created for photoacoustic spectra as well as for dynamic difference spectra of polymers under periodic external mechanical perturbation. From the positions and signs of cross peaks in the 2D-maps the relative direction and timing of reorientational motions can be determined Depth profiling has been demonstrated on ethylene-vinyl acetate copolymer on polypropylene. The effects of mechanical stress on polymers using 2D-FT-IR of have been shown for isotactic polypropylene and a polyesther/polyurethane block copolymer.

Two approaches to NMR analysis of mixtures used in Bruker instruments are considered: (1) a combination of high-performance liquid chromatography, NMR, and mass spectrometry, (2) the use of specialized software and spectral databases.

The concentrations of HF and HCl in the lower stratosphere have been monitored by high resolution FT-IR spectroscopy. In addition to their long term increase regular seasonal variations with a maximum in the early spring have been observed. These variations are correlated with the polar vortexes and transferred to lower latitudes by atmospheric circulations.

Kinetics of electrochemical reduction of trialkylphosphates, slow homogeneous electron transfer reaction with the participation of paramagnetic intermediates and multispin Co(II)-, Cu(II)-, Zn(II)-nitroxyde radical systems reduction processes are studied with the help of combining electrochemical method and EPR.

NMR experiments in solid caesium perbromate have recently been performed at magnetic fields of 1.88 T and 7.04 T together with spectral simulations for 79Br, 81Br and 133Cs in solid caesium perbromate. The line shapes are dominated by quadrupole effects. For bromine the quadrupole asymmetry parameter [η] is observed to be zero at all temperatures while the quadrupole coupling constant (CQ) as a function of temperature shows two approximately linear regions on either side of a non-linear region between 200 K and 260 K where an extended orientational phase transition occurs. 133Cs shows an increase of CQ and a decrease of η with increasing temperature. This behaviour may be associated with an anisotropic change of the “a” lattice parameter.

A new method of diffusion coefficient measurement in liquids under electrolysis is considered. It is shown that the diffusion parameters can be correctly determined from the dependence on the electrolysis time of the EPR signal intensity of the ion radicals formed.

The127I and133Cs NMR spectra of polycrystalline CsIO4, a material of potential interest for transformation of laser irradiation, have been measured in the temperature range 170–440 K and the line shape has been analyzed taking into account first and second order quadrupole interactions and chemical shift anisotropy. Quadrupole coupling constants and asymmetry parameters have been determined as a function of temperature.127I and133Cs data consistently show two phase transitions in the ranges 243–300 K and 420–440 K with a temperature hysteresis for the first transition and a range for coexistence of two phases. The time evolution of the NMR signal suggests the existence of piezomagnetism, which was believed to exist only in crystals with a magnetic structure.

Changes in X-nuclei screening and scalar spin-spin X-H(D) coupling constants induced by the H-D substitutions in isotopomers [XH4-nDn] (X = N, Al, Ga) have been determined by 14,1l5N, 27 AI, 69,71Ga NMR. Isotopic chemical shifts of nuclei 51V, 53Cr, 99Tc induced by the 16O-18O substitution have been measured for tetra-oxo complexes [VO4]3-, [CrO4]2-, and [TcO4]-. The deuterium-induced secondary isotopic effect on the screening constant of the X nuclei and the scalar spin-spin X-H(D) coupling are correlated with the X-H bond length in [XHJ for the row X = N, C, B, Al, Ga, As the internuclear X-H distance increases, the isotopic shift of the X nuclei with respect to the signal from [XHJ rises linearly on H-D substitution from a negative value for [NH4]+, CH4 to a positive value (the downfield shift) for [GaH4]-. When D is substituted for H in [XH4] the X-H spin-spin coupling constant decreases for X = N, C, B, Al, Ga (the secondary isotopic effect). The magnitude and sign of the secondary isotopic effects on the screening constants of the X nuclei in [XH4] and [XO4] depend on the atomic number of the X element. With the increasing atomic number in the period the isotopic shift to high field rises in magnitude, while with the increasing atomic number in the group the isotopic upfield shift drops in the absolute value and can even change sign in the substitution of the ligand light isotope by a heavier isotope.

The1H-,17O- and 13C-spectra of 17O-enriched H2O were measured in different solvents at frequencies up to 360 MHz.In acetone the 1H-2H-coupling and the 1H isotopic shift due to deuterium and carbon are determined and the 1H-17O-coupling is calculated.From the 17O-exchange between acetone and water the carbon isotopic shift due to oxygen is determined.

AbstractDie Kernresonanzspektren isotherm kristallisierter Proben von Polyäthylenterephthalat wurden vor und nach der Quellung in deuteriertem Aceton als Funktion der Temperatur gemessen. Anschließend wurde jedes Spektrum in eine breite und eine schmale Komponente zerlegt. Es zeigt sich, daß durch die Quellung der Einfrierbereich verbreitert und die Einfriertemperatur erniedrigt wird. Diese Erniedrigung ist von den Kristallisationsbedingungen unabhängig. Die Linienbreite der schmalen Komponente wird durch die Quellung leicht erhöht, was für eine Zunahme der Kettenverspannung in den nichtkristallinen Bereichen spricht. Das zweite Moment der breiten Komponente wird durch die Quellung erniedrigt. Daraus wird geschlossen, daß das Quellmittel auch in die Kristallite eindringt.Des weiteren wurde eine Probe unmittelbar durch Quellung kristallisiert. Bei dieser Probe beobachtet man eine besonders kleine Linienbreite der schmalen Komponente. Dies wird durch den höheren Quellmittelgehalt der Probe sowie durch eine relativ geringe Verspannung der Ketten in den nichtkristallinen Bereichen erklärt. Beides ist eine Folge des besonderen Mechanismus der Quellungskristallisation.

The NMR-line obtained with polyethyleneterephthalate is separated in a broad and in a narrow component by means of a special method based on several measurements of the line with different modulations. From the areas under the two components the fraction of material performing a mikrobrownian motion is determined. This fraction is extrapolated to infinit temperatures by using a theory based on free volume. The extrapolated movable fraction is smaller than the noncrystalline fraction determined from density. This is explained by the fact that some chains in the noncrystalline regions are nearly extended forming a „rigid”︁ noncrystalline fraction. For samples quenched from crystallization temperature this fraction is larger than for samples cooled down slowly. Plotted as a function of crystallization temperature the rigid noncrystalline fraction is at maximum at about 200°C.

Eine Monomereinheit von Polyäthylenterephthalat besteht aus zwei Vier-Spinsystemen, nämlich aus den vier Protonen des Benzolringes und den vier Protonen der C2H4-Gruppe. DieSchrödinger-Gleichung für die beiden Vier-Spinsysteme wurde gelöst, sowohl für den Fall, daß diese starr angeordnet sind, als auch für den Fall, daß sie rotieren. Die Wechselwirkung eines jeden Vier-Spinsystems mit der Umgebung wurde durch eine Verbreiterung der Einzellinien zuGaußkurven berücksichtigt. Die berechneten Kurven konnten an die gemessenen angepaßt werden. Dabei wurden die Verbreiterungsparameter und die Anteile der Gruppen, die jeweils rotieren, in Abhängigkeit von der Temperatur bestimmt.