bluuebunny/crossref_metadata_2025 huggingface dataset:
Die Druckabhängigkeit des Wärmeleitvermögens und die Bildung von Doppelmolekeln von Äthylbromid
Authors: Edwards J. , Puebla C.
Published: September 2012

Nach der von Schäfer und Foz Gazulla [1] beschriebenen Methode wird die Zahl der Doppelmolekeln von Äthylbromid aus der Abhängigkeit der Wärmeleitfähigkeit vom Druck oberhalb von 50 Torr ermittelt. Die Ergebnisse werden dazu benutzt, eine Darstellung des zweiten Virialkoeffizienten anzugeben.
Photochemistry of Biologically Important Transition Metal Complexes. I. Cyanocobalamin and Related Corrin Complexes of Rhodium(III)
Authors: Vogler A. , Hirschmann R. , Otto H. , Kunkely H.
Published: September 2012

The quantum yield of the well known photoaquation of cyanocobalamin (vitamin B12) was determined (ϕ ˜ 10−4) and was found to be independent of the irradiating wavelength. In addition cyanocobalamin did not show the characteristic corrin phosphorescence. In agreement with an earlier suggestion it is concluded that the excitation energy initially absorbed by the corrin ligand is rapidly transferred to a reactive excited LF state which lies below the lowest corrin triplet. This conclusion is supported by the behavior of corrin complexes of Rh(III). Contrary to cyanocobalamin the complex dicyanorhodium(III)‐corrin did not undergo a photoaquation but has been shown to emit a strong corrin phosphorescence. These observations are consistent with the assumption that the lowest excited LF state lies now well above the lowest corrin triplet. If both axial cyanide ligands which have a strong field are replaced by the weak‐field ligand chloride the energy of the lowest excited LF state should drop considerably. The behavior of dichlororhodium(III)‐corrin indicates that the lowest corrin triplet lies only slightly below the lowest excited LF state which is responsible for the photoreactivity. The reactive LF state may be populated from the lowest corrin triplet by thermal activation. At 77 K dichlororhodium(III)‐corrin showed a strong corrin phosphorescence. At room temperature this emission was essentially quenched and the complex underwent a photoaquation.
Photochemistry of Biologically Important Transition Metal Complexes. II. Carbonylpiperidinetetraphenylporphine Complexes of Iron(II) and Ruthenium(II)
Authors: Vogler Arnd , Kunkely Horst
Published: September 2012

Carbonylpiperidinetetraphenylporphineiron(II) and dipiperidinetetraphenylporphineiron(II) do not emit the characteristic porphyrin phosphorescence. It is suggested that the porphyrin singlets initially excited undergo an efficient radiationless transition to an excited state which lies below the lowest porphyrin triplet. It is concluded that this lower excited state initiates the release of coordinated CO which has been observed for a variety of biologically important carbonylporphyrins of iron(II). It is assumed that the reactive state is either an excited CT or, more likely, a LF state. If iron(II) is replaced by the homologous ruthenium(II) the lowest LF excited state lies apparently at higher energies than the lowest porphyrin triplet due to the larger LF splitting of the heavier ruthenium. Hence carbonylpiperidinetetra‐phenylporphineruthenium(II) dissolved in piperidine shows the typical porphyrin phosphorescence, but undergoes also a simultaneous photosubstitution of CO by piperidine with low efficiency. Quantum yields of CO release and relative emission intensities were determined at two irradiating wavelengths (412 and 530 nm) and at two temperatures (25 °C and 80 °C). The results led to the suggestion that the reactive LF state can be populated from the lower porphyrin triplet by thermal activation. In addition to this thermally activated photolysis a temperature independent contribution seems to be important at higher excitation energies. It is assumed that the deactivation cascade starting from higher excited singlets of the porphyrin ligand includes the population of the reactive LF state before the lowest porphyrin triplet is reached. It is also possible that it is not a LF state but a low‐lying CT state which is responsible for the photoreactivity.
Radikale aus der Oxidation von Essigsäure‐2‐hydroxyäthylester. Eine in situ‐ESR‐Studie
Authors: Behrens G. , Schulte‐Frohlinde D.
Published: September 2012

Die ESR‐Spektren von freien Radikalen aus der Reaktion von OH‐Radikalen, tert.‐Butoxyl‐Radikalen und Aceton Tripletts mit Essigsäure‐2‐hydroxyäthylester wurden in verschiedenen Lösungsmitteln untersucht. Die drei durch H‐Atom Abstraktion zu erwartenden Radikale wurden identifiziert (CH2C(O)OCH2CH2OH (2), CH3C(O)OCH‐CH2OH (3), CH3C(O)OCH2CH‐OH (5)). Ferner werden die Hyperfeinaufspaltungen von vier Adduktradikalen mitgeteilt, die in Sekundärreaktionen durch Addition von β‐Oxoalkyl‐ und tert.‐Butoxylradikalen an intermediär erzeugte Enole entstehen (CH3C(OH)CH2CH2CHO (7), CH(OH)CH2CH2CHO (8), CH3C(OH)CH2CH2COCH3 (11), CH3C(OH)CH2‐OC(CH3)3 (12). Die OH‐Kopplungen dieser Radikale konnten aufgelöst werden. Sie sind lösungsmittelabhängig und zeigen bei bestimmten Temperaturen einen Nulldurchgang.

In wäßrigen Lösungen zerfällt das Radikal 5 in Essigsäure und das Formylmethylradikal (4). Beim Übergang von Wasser auf organische Lösungsmittel wird die Lebensdauer von 5 um ca. drei Größenordnungen verlängert. Die Zusammenhänge zwischen Konformation und Größe der Hyperfeinaufspaltungen werden für das Radikal 5 diskutiert. Das Auftreten ungewöhnlich kleiner β‐Kopplungen, gut auflösbarer ε‐Aufspaltungen und selektiver Linienverbreiterungen werden auf Polarisation des Radikals und eine intramolekulare Rotations‐barriere zurückgeführt. Aus den Linienverbreiterungen wurde die Barriere zu ≥ 2,4 kcal mol−1 berechnet. Diese Polarisation könnte die heterolytische Dissoziation des Radikals in polaren Lösungsmitteln erleichtern.
Redoxkinetik von Metallkomplexen in nichtwäßrigen Lösungen I. Die Reduktion von [Fe(OH2)6]3+ mit Fe(II) in Nitromethan, Acetonitril und Propandiol‐1,2‐carbonat
Authors: Schmid R. , Sapunov V. N. , Gutmann V.
Published: September 2012

Lösungen von Hexaquo‐eisen(III) in schwach koordinierenden Lösungsmitteln enthalten neben hexakoordiniertem (inaktivem) [Fe(OH2)6]3+ (Fei3+) auch eine pentakoordinierte (aktive) Spezies (Fea3+), bei der ein Molekül H2O outer‐sphere‐komplex gebunden ist. Fea3+ steht mit Fei3+ im Gleichgewicht und wird tausendmal schneller als dieses reduziert. Daneben tritt auch in kleiner Konzentration ein tetrakoordinierter Komplex auf, der noch aktiver als Fea3+ ist. Die Geschwindigkeitskonstanten der Reduktion sowie der Gleichgewichtseinstellung Fei3+ → Fea3+ und die Gleichgewichtskonstante [Fea3+]/[Fei3+] zeigen eine starke Abhängigkeit vom Solvens, die den unterschiedlichen Outer‐sphere‐Effekten der Lösungsmittel zugeschrieben wird.
A Deuteron Magnetic Resonance Study of Tantalum Deuterides
Authors: Roenker K. P. , Barnes R. G. , Brooker H. R.
Published: September 2012

Tantalum deuterides in the composition range TaD0.43–TaD0.76were investigated by means of deuteron nuclear magnetic resonance over the temperature range from 4.2 to 400 K. The β‐α phase transition, in the temperature range 320–370 K for these compounds, is sharply defined by the extinction of the deuteron quadrupole interaction when the cubic α phase is reached. These results are discussed in relation to other determinations of the β‐α transition temperature. No other significant changes in the NMR spectrum are observed, down to 4.2 K, at which temperature the quadrupole coupling constants are equal, within the experimental uncertainty, having the value,e2qQ/h= 33.9 ± 0.7 kHz, independent of composition. The asymmetry parameter values, however, tend toward zero with increasing deuterium content. It is noted that the thermal width of the β‐α transition is increased by high oxygen content of the tantalum metal.
Untersuchungen über das Adsorptionsverhalten von Xenon und Krypton an Aktivkohle
Authors: Halblaub K. , Schäfer K.
Published: September 2012

Mit Hilfe eines neuentwickelten, hochempfindlichen Kalorimeters wurden bei 80 und 294 K die Adsorptionswärmen von Xenon und Krypton an Aktivkohle experimentell ermittelt. Diese werden berechneten Wärmen gegenübergestellt und ihre Temperaturabhängigkeit im Bereich zwischen 80 und 403 K diskutiert. Anschließend werden die Ergebnisse im Hinblick auf die Dubininsche Theorie interpretiert.
Zur Elektronenstruktur hochsymmetrischer Komplexe der Lanthanoiden und Actinoiden III. “Elektronisches” Raman‐Spektrum von Cs2U(IV)Cl6 [1]
Authors: Amberger H.‐D. , Fischer R. D. , Rosenbauer G. G. , Spiegl A. W.
Published: September 2012

Neben den reinen Schwingungs‐Raman‐Banden weist das Tieftemperatur‐Raman‐Spektrum von Cs2U(IV)Cl6 einige weitere Signale auf, deren Auftreten von der Wahl der Erregerlinie weitgehend unabhängig ist und die wir deshalb “elektronischen” Raman‐Effekten zuschreiben. Unterstützt wird diese Ansicht auch dadurch, daß diese Signale jeweils entweder in unmittelbarer Nähe von absorptionsspektroskopisch direkt beobachteten Banden liegen oder sich innerhalb enger Energiebereiche bewegen, in welchen aufgrund kristallfeldtheoretischer Berechnungen Kristallfeld‐Niveaus zu erwarten sind. Sowohl die Zahl als auch die relative Gruppierung der elektronischen Raman‐Banden weisen darauf hin, daß das U4+‐Zentralion einem effektiven Kristallfeld niedriger Symmetrie ausgesetzt ist.
Infrarotspektren von Übergangsmetallkomplexen und von Aziden unter hohen Drücken
Authors: Klopsch A. , Hellner E. , Dehnicke K.
Published: September 2012

Teile der IR‐Spektren einiger Metallcarbonyle, Cyclopentadienylmetallcarbonyle, des Na2[Fe(CN)5NO]· 2H2O sowie von KN3 und AgN3 unter Drücken bis ∼ 30 kbar werden mitgeteilt. Im Gegensatz zu den früher untersuchten Cyanokomplexen erweisen sich die Metallcarbonyle als sehr druckresistent bezüglich ihrer Symmetrie, was mit den unterschiedlichen Bindungsverhältnissen erklärt wird. Am Beispiel des {[(C6H5)3P]2Ru(CO)2J2}‐ Komplexes kann die Frage der Anordnung der CO‐Liganden mittels ihrer Druckabhängigkeit zugunsten der cis‐Stellung entschieden werden. Das komplexe Anion von Na2[Fe(CN)5NO]· 2H2O erreicht unter Druck die höchstmögliche Symmetrie C4ν. Bei den Aziden KN3 und AgN3 ließ sich durch die Beobachtung der Kombinationsschwingung (νas + νasN3) eine starke Druckabhängigkeit der IR‐inaktiven νasN3 feststellen.
A Simple Dissipation Model for Collisional T‐V Energy Transfer and Association Processes between Atoms and Polyatomic Molecules. I. Analytical Approximations for the Case of a Morse Interaction
Authors: Siré E. O. , Kohlmaier G. H.
Published: September 2012

A simple classical phenomenological Markoffian damping model for the collisional T‐V energy transfer of a gas atom impinging on a “surface”‐atom of a polyatomic molecule or a solid lattice surface is proposed. The relevant dynamical features of the polyatomic system, projected onto the collisional axis, are taken to be reduced to a local (surface oscillator) and to a dissipating (damping) part. In the context of a new approximate renormalizing procedure for the calculation of T‐V energy transfer, analytical results were derived for the case of a intermolecular Morse potential in a wide velocity range. We have shown that the existence of a V‐V intramolecular dissipative mechanism can strongly influence the velocity dependence on the energy transfer. Different effects due to the intermolecular dissipating forces were observed for the energy transfer in the impulsive and languid collisional regime.
The Temperature Dependence of the Electrolytic Dissociation of Some 1‐Hydroxy‐alkyl Radicals in Aqueous Solution (a Pulse Radiolysis Study)
Authors: Toffel P. , Henglein A.
Published: September 2012

Various simple aliphatic and cycloaliphatic 1‐hydroxyalkyl radicals were produced in aqueous solution and their extinction coefficients (250 to 450 nm) and pK‐values determined. The dependence of the pK‐value on the temperature was studied in the range from 2 to 64°C. The enthalpy of the electrolytic dissociation is slightly higher for the cyclic radicals than for the non‐cyclic ones. This effect is explained by differences in the solvation energy of the radical anions. The entropy of the electrolytic dissociation is always negative, but markedly lower for the cyclic radicals having small rings. The rate constant of addition of the hydrated electron to various cyclic ketones has also been determined at different temperatures. The activation energies of these reactions are lower than that of the mobility of the hydrated electron. This effect is interpreted by a decrease in the collision diameter with increasing temperature. The temperature dependence of some electron transfer reactions of 1‐hydroxycycloalkyl radicals with nitrobenzene and ferrihexacyanide was also investigated.
Polarized Absorption and Photoelectron Spectra of Aceheptylene, 3.5‐Dimethylaceheptylene and 3,5,8,10‐Tetramethylaceheptylene
Authors: Bischof Peter , Gleiter Rolf , Hafner Klaus , Kobayashi Michio , Spanget‐Larsen Jens
Published: September 2012

UV‐visible polarized absorption spectra of aceheptylene (1), 3,5‐dimethylaceheptylene (2) and 3,5,8,10‐tetramethylaceheptylene (3) have been measured at 77 K in stretched polyethylene sheets. PPP‐CI calculations of transition energies, oscillator strengths and polarization directions are in good agreement with the first ten transitions.

In the photoelectron spectra of 1, 2 and 3 the first four bands could be assigned to π orbitals on the basis of semiempirical calculations. The energy level scheme and the polarization of the transitions of 1 can be understood in terms of a HMO interaction diagram between heptalene and ethylene.
Ageing Effects in Monomolecular Oxide Layers on Gold
Authors: Schultze J. W. , Lohrengel M. M.
Published: September 2012

Ageing effects in monomolecular oxide layers on gold electrodes were investigated by fast potentiostatic pulse techniques.

Oxide layers of various coverages were formed at a potential Ep within 1 ms and aged at a potential εp for ageing times between 1 ms and 1000s. Finally, the oxide was reduced potentiodynamically with 500 V s−1.

With increasing ageing the reduction peaks show an increasing current and a decreasing half width. At low coverages, formed at low potentials εp, the vanishing of an unstable species and the growth of a stable oxide can be separated. At larger coverages, the increasing homogeneity of the layer can be observed only, because these effects are smeared out. Variations of εa, show that the ageing process depends on the potential. A mechanism is discussed which includes the cathodic reduction of the unstable species and the anodic formation of the stable oxide. The unstable species is probably O2‐ or OH− adsorbed reversibly.
Der Einfluß des Partialdruckes auf die Geschwindigkeit der kathodischen Sauerstoffreduktion
Authors: Fabjan Ch. , Azizian M.
Published: September 2012

Der Einfluß des Partialdruckes auf die Geschwindigkeit der kathodischen Sauerstoffreduktion wurde an blankem Platin in saurem und alkalischem Elektrolyten und an Graphit in alkalischer Lösung untersucht. An Platin wird in beiden Fällen eine kathodische Reaktionsordnung von +1,0 ermittelt, während an Graphit ein Wert von +0,5 gefunden wird. Dieses Ergebnis erlaubt eine Formulierung des Reaktionsmechanismus in der Weise, daß an Platin die Reduktion des molekularen Sauerstoffes im Durchtrittsbereich direkt zu Wasser bzw. OH−‐Ionen führt, wobei kein Wasserstoffperoxid als stabiles Reaktionsprodukt entsteht:

Für alkalische Elektrolyte:

magnified image

An Kohlematerial (Graphit) führt die Reaktion in alkalischem Medium ausschließlich zur Bildung von Peroxid.
Die Reaktion von F‐Atomen mit HCl
Authors: Wagner H. Gg. , Warnatz J. , Zetzsch C.
Published: September 2012

Die Temperaturabhängigkeit der Geschwindigkeitskonstanten der schnellen Reaktion

wird in einem Strömungssystem mit massenspektrometrischer Analyse gemessen. Als Ergebnis erhält man

zwischen 250 K und 370 K.
Magnetische Resonanzuntersuchungen zur Struktur, Kinetik und Hyperfeinwechselwirkung des Systems Nitroxidradikal‐Wasser
Authors: Meise Karin , Müller‐Warmuth W. , Nientiedt H.‐W.
Published: September 2012

Wäßrige Lösungen von drei verschiedenen organischen freien Nitroxidradikalen wurden zwischen 0 und 100°C mit magnetischen Resonanzmethoden untersucht. Messungen der Protonenrelaxationsraten zwischen 0,75 und 60 MHz lieferten Aussagen über die zwischenmolekularen Wechselwirkungen. Aus der dynamischen Kernpolarisation im schwachen Magnetfeld konnte auf die dipolaren und skalaren Relaxationsanteile geschlossen werden. Weiter wurden chemische Kontaktverschiebungen der Protonen bei 270 MHz beobachtet, um in Kombination mit den anderen Daten die Bildungskonstanten des Komplexes Nitroxid‐Wasser und die Hyperfeinkopplungskonstante über die Wasserstoffbrücke zu ermitteln. Detaillierte Angaben werden über die Lage des Gleichgewichtes, die Lebensdauer der Wasserstoffbrücke, und die einzelnen Bewegungsprozesse gemacht.
The Solvolysis of Tetranitromethane in Various Polar and Nonpolar Solvents
Authors: Frank A. J. , Henglein A.
Published: September 2012

Tetranitromethane yields nitroform upon its thermal decomposition in water, alcohols, acetone and n‐hexane. The rate constant of nitroform formation was determined by measuring the absorbance of the nitroform anion C(NO2)3− as a function of reaction time. The decomposition in water proceeds with an activation energy of 1.6 eV and an Arrhenius factor of 1017.8 s−1 which is of similar magnitude to that obtained in the gas phase thermolysis of tetranitromethane. Two mechanisms involving heterolytic CN bond rupture in water and homolytic CN bond cleavage in the less polar solvents are proposed to account for the solvolysis reactions. In the latter case, this leads to the formation of the trinitromethyl radical C(NO2)3, which, because of its unusually high electron affinity, is able to abstract an electron from the alcohols and acetone; in n‐hexane, the main reaction path involves hydrogen atom abstraction by the radical. Above pH 6 in aqueous solution, the rate of hydrolysis is markedly catalyzed by OH− anions.
A Proton Magnetic Resonance Study of Ionic Association in Aqueous and Nonaqueous Solutions of Tetraalkylammonium Salts
Authors: Kabisch G.
Published: September 2012

The behaviour of the alkyl proton resonances of symmetrical tetraalkylammonium ions is studied in aqueous and nonaqueous salt solutions. Information about ion‐pairing can be obtained by investigating the relative chemical shift Δδ = δCH2(1) ‐ δCH3 of the cationic protons as a function of concentration, temperature, and anion. In organic solvents cation‐anion association is evident from our experimental data. The corresponding equilibrium constants could be determined for several TAA salts in acetonitrile solution. In aqueous solution the association behaviour is a more complex one. It seems that at low and medium concentrations cation‐cation interactions are dominant, whereas in concentrated solutions multiple ion aggregates involving anions are formed.
Pressure Dependence of the Selfassociation of 9‐Methylpurine in Aqueous Solution
Authors: Gaarz U. , Lüdemann H.‐D.
Published: September 2012

The selfassociation of 9‐methylpurine (9‐MP) in aqueous solution has been studied by analysis of the proton chemical shift concentration dependence at pressures up to 1500 bar. To this purpose a high pressure glass cell has been developed, fitting into the standard receiver coil of a high resolution NMR spectrometer. The influence of pressure on the UV‐spectra of 9‐MP has been measured. Pressure favours self association of 9‐MP. The thermodynamic data derived from an isodesmic association model are:

K (1 bar, 20°C) = 1.4 mol−1; K (1500 bar, 20°C) = 1.8 mol−1; ΔH (van't Hoff) = ‐(9.6 ± 1)kj·mol−1 and ΔV = ‐(4.0 ± 1.0)cm3 · mol−1.
Transport Properties of Nine Binary and Two Ternary Mixtures of Gases at Low Density
Authors: Kestin J. , Ro Sung Tack
Published: September 2012

The paper analyses earlier data on the viscosity of binary and ternary mixtures in terms of the extended law of corresponding states due to Kestin, Ro, and Wakeham (KRW). The binary mixtures involve CO2 and CH4 with each other, and each with He, Ne, Ar, N2. The ternary mixtures are: N2ArCO2 and CH4N2CO2.

Measurements fully corroborate the efficiency of the KRW law for the calculation of viscosity and binary diffusion coefficient of the simpler polyatomic gases, as expected from theory.

The paper contains short tables of the viscosity and binary diffusion coefficients for the nine binary systems under consideration.
Zur Bestimmung der Beweglichkeit von Kohlenwasserstoffmolekülen auf Katalysatoroberflächen mittels Neutronenstreuung
Authors: Stockmeyer R.
Published: September 2012

Die Intensitätsverteilung von langsamen Neutronen, die an adsorbierten Kohlenwasserstoffmolekülen gestreut worden sind, enthält Informationen über die Bewegung der Moleküle. Hier wird das Streugesetz für inkohärent streuende Moleküle unter Berücksichtigung der sehr verschiedenen Beweglichkeit senkrecht und parallel zur Oberfläche abgeleitet. Im Gegensatz zu dem bekannten Streugesetz von dreidimensional diffundierenden Teilchen divergiert das Streugesetz für zweidimensional diffundierende Moleküle logarithmisch für verschwindenden Energieübertrag. Die sich daraus ergebenden Konsequenzen für die Interpretation von Neutronenstreudaten werden diskutiert.
Spektroskopische Untersuchungen an Merocyaninen II. Blitzspektroskopische Untersuchung der thermischen cis → trans‐Isomerisierung der malodinitril‐substituierten vinylogen Säureamide
Authors: Joerges Eike , Schneider Siegfried , Dörr Friedrich , Daltrozzo Ewald
Published: September 2012

Offenkettige Merocyanine zeigen eine photoinduzierte trans → cis‐Umlagerung, der eine thermische cis → trans‐Rückumwandlung folgt. In dieser Arbeit wird die thermische cis → trans‐Isomerisierung der malodinitril‐substituierten vinylogen Säureamide blitzphotometrisch als Funktion von Temperatur und Lösungsmittel untersucht. Die Abhängigkeit der Aktivierungsparameter von der Polarität des Lösungsmittels und der Länge der Merocyanine wird anhand quantenmechanischer Modellrechnungen diskutiert.
Near Infrared Absorption of Ethylene between 5500 cm−1 and 6500 cm−1 to High Pressures and Temperatures
Authors: Buback M. , Nees F. W.
Published: September 2012

The near infrared absorption of pure ethylene in the region of the first overtones of the CH stretching fundamentals (5500 cm−1 to 6500 cm−1) was measured at supercritical temperatures (Tc = 9.5°C) between 22°C and 200°C from 0.05 to 3000 bar.

Density and temperature dependence of bandshape, maximum frequency and absorption intensity are reported. The bands observed within a wide range of experimental conditions are assigned to combinations and overtones of vibrations. At high densities pressure induced (“forbidden”) bands occur.

The molar integrated absorption intensity of the strong ν5 + ν9 combination band at 6138 cm−1 is independent of pressure and temperature. This enables spectroscopic concentration determinations on ethylene in high pressure‐high temperature equilibria and reactions.
Entmischungserscheinungen in Pd  B‐Legierungen
Authors: Brodowsky H. , Schaller H.‐J.
Published: September 2012

Unterhalb einer kritischen Temperatur von 410°C existiert in der festen Lösung von Bor in Palladium eine Mischungslücke, deren Grenzzusammensetzungen bei 312°C röntgenographisch zu PdB0,021 und PdB0,114 ermittelt wurden. Die Mischungslücke ergibt sich in guter Näherung durch die Auswertung eigener Aktivitätsmessungen bei 1000°C; dabei wurden die Überschußpotentiale des Bors analog wie diejenigen des Wasserstoffs im Palladium durch zwei Effekte gedeutet: Durch den Anstieg der Fermi‐Energie beim Übertritt der äußeren Bor‐Elektronen in das Elektronengas des Metalls sowie durch eine Attraktionswechselwirkung der Zwischengitteratome, die durch die Gitterverzerrung hervorgerufen wird.
Keimbildung und Kristallwachstum bei der elektrolytischen Abscheidung von Kupfer‐Zink‐Legierungen
Authors: Randig H.‐J. , Lacmann R.
Published: September 2012

Es werden experimentelle Untersuchungen der elektrolytischen Abscheidung von Kupfer‐Zink‐Legierungen auf Platineinkristallkathoden beschrieben. Der Kupfergehalt der Legierungen, die aus cyanidischen Lösungen abgeschieden wurden, nimmt mit zunehmender Überspannung zunächst ab, durchläuft ein Minimum und steigt dann wieder an. In einigen Fällen treten in den Kurven Stufen auf, die dem Übergang zwischen den Messingphasen entsprechen. Die Kupfer‐ und Zinkteilstromstärken streben im Gebiet des Minimums des Kupfergehaltes Grenzwerten zu.

Die Meßergebnisse können theoretisch mit Keimbildungsvorgängen erklärt werden, die bei hoher Stromdichte zusätzlich durch vorgelagerte chemische Reaktionen gehemmt werden.
Thermodynamic Properties and Structure of Liquid Alloys
Authors: Predel Bruno
Published: September 2012

The direct correlation between the atomic structure of liquid alloys and their thermodynamic properties makes it possible in principle to obtain information about the structure changes that occur as a result of alloy formation. It is first shown that in addition to the change of the bond properties atomic volume differences of the alloy partners have a definite influence on the energetics of alloy formation. Furthermore a model is developed which successfully explains the deviations from regular behavior of some alloy systems with tendencies toward compound formation by postulating the existence of regions with special coordination relationships in the melt which are in a dynamic equilibrium with statistically disordered regions. Finally, it is suggested that the tendencies of some alloys to form metastable glass like phases are related to the tendencies of these alloys toward the prevailing formation of bonds between atoms of the different species.
Measurement of the Structure Factor of Liquid Rubidium by Neutron Diffraction up to 1400 K and 200 bar
Authors: Block R. , Suck J. B. , Gläser W. , Freyland W. , Hensel F.
Published: September 2012

The structure factor S(Q) of liquid rubidium has been measured by neutron diffraction in the temperature range between 450 K and 1400 K corresponding to a density change from 1.42g/cm3 to 0.98 g/cm3. Measurements have been performed with a diffractometer for elastic diffuse scattering of neutrons at the high flux reactor in Grenoble. To avoid evaporation of the liquid metal at high temperatures; a new technique had to be developed. A detailed description is given of the experimental set‐up which is suitable for neutron diffraction measurements of corrosive liquids at elevated temperatures and pressures. It is the first time that neutron diffraction measurements on a liquid metal have been extended to these combined conditions of high temperature–high pressure, as are reported in this paper.

The momentum transfer Q covered in this investigation ranges from 0.2 Å−1 to 2.4 Å−1. As a function of temperature and density the following significant changes in S(Q) have been observed:

the height of the first maximum decreases from about 2.0 at 450 K to 1.12 at 1400 K;

in the same temperature limits S(Q) at the lowest Q‐values measured increases by a factor of 6;

a clear shift in the position of the first maximum from 1.525 Å−1 to 1.43 Å−1 is found.

Up to 1200 K three different pressures, saturation pressure, 100 bar, and 200 bar have been studied. Corresponding to the relatively small compressibility of liquid rubidium at these temperatures, no appreciable pressure dependence of S(Q) at the different constant temperatures was observed. The accuracy of the measured structure factor data is chequed at low Q‐values by a comparison of compressibilities of liquid rubidium determined from recent density measurements with those extracted from our S(Q)‐values according to the Ornstein‐Zernike relation.
Untersuchungen zum Halbleiter‐Metall‐Übergang von Schmelzen im System Ge As Te. I. Elektrische Leitfähigkeit
Authors: Schnurnberger W. , Thurn H. , Krebs H.
Published: September 2012

Die elektrische Leitfähigkeit von Schmelzen der binären Systeme Ge  Te und AsTe sowie der ternären Schnitte Ge5AsxTe95‐x und Ge15AsxTeg85‐x wurde mit einer verbesserten elektrodenlosen Meßmethode bis 1000°C untersucht. Alle Schmelzen zeigen bei hohen Temperaturen ein sehr ähnliches, nahezu metallisches Verhalten. Mit abnehmender Temperatur erfolgt ein Übergang zu halbleitendem Verhalten, der bei glasig erstarrenden Proben besonders ausgeprägt ist. Dieser Übergang ist eine Folge der Änderung des Bindungssystems und damit der Nahordnung der Atome in der Schmelze. Die dadurch bewirkte Änderung der Bandstruktur führt zu besonders hohen Werten der Aktivierungsenergie des elektrischen Widerstandes im Übergangsgebiet.
Catalysis on Liquids Metals
Authors: Schwab Georg‐Maria
Published: September 2012

The rate and activation energy of formic acid dehydrogenation over liquid metals, especially mercury, tin and thallium and their alloys, are studied. The results suggest that beside the usual electronic effects covalent bonds and Friedel‐terms may occur in liquid alloys. The validity of the compensation effect for a reaction catalysed by these alloys shows that also in solid catalysts this effect is not necessarily a consequence of the presence of “active centers”.
Stability Function of Antimony‐Chalcogen Melts
Authors: Blachnik R. , Bolte G.
Published: September 2012

The activities of chalcogen were determined in molten mixtures of antimony‐sulphur and antimony‐tellurium by a modified dew‐point method. These data and literature data were used to derive the stability function δ2ΔG/δx2 which indicates the formation of associates at a composition of 60 atom per cent chalcogen in the liquid state. These associates with polymeric bonding systems are of different structure and bonding strength and thus influence the topology of the Vb‐Vlb phase diagrams.
Metal Nonmetal Transitions in Fluid Systems
Authors: Hensel F.
Published: September 2012

A brief review is presented of the continuous metal‐nonmetal transition observed in different fluid systems, with special reference to expanded fluid metals, fluid selenium and fluid binary semiconducting alloys. Recent experimental results are discussed and compared with recent theoretical speculations.
Electrical Conductivity and Thermopower of Metal Ammonia Solutions
Authors: Hahne S. , Krebs P. , Schindewolf U.
Published: September 2012

Data of equivalent conductivity of sodium ammonia solutions in a wide concentration, temperature and pressure range prove that the nonmetal‐metal transition is favoured by increasing temperature and disfavoured by increasing pressure. Some data on the temperature dependence of the thermopower support the concept of activated transport (semiconduction) in the transition range, although the combination of thermopower and conductivity data does not follow the simple theory of semiconductors. In conclusion it is shown that the conductivity behaviour of metal ammonia solutions can be explained by a homogeneous chemical equilibrium between solvated electrons (electrolytic conduction) and free electrons (metallic conduction) which as usually depends on concentration, temperature and pressure.
Ionic Conductance in Liquid Cesium Gold Alloys
Authors: Krüger K. D. , Schmutzler R. W.
Published: September 2012

The paper presents experimental data of the electromigration in liquid Cs‐Au alloys at the stoichiometric composition. The experiments were performed at 65°C, i.e. about 60°C above the melting point of the compound, with a modified capillary technique. A simple model allows to evaluate the correlation of current induced atom or ion transport to the total charge transported through the specimen. It is found that one Cs‐ion is transported per elementary charge into the cathode compartment within experimental error of about ± 25%, which is exactly the value required by the Faraday law of electrolyses in ionic conductors. It is therefore concluded, that the stoichiometric liquid CsAu alloy consists essentially of Cs+ and Au− ions.
Concentration Fluctuations in Solutions of Potassium in Potassium Bromide. A Neutron Small Angle Scattering Investigation in the Non Metal to Metal Concentration Range
Authors: Jal J. F. , Chieux P. , Dupuy J.
Published: September 2012

A preliminary study of the concentration fluctuations in solutions of K in KBr has been performed by small angle neutron scattering in the non metal to metal transition concentration range. Approximate values of the correlation length of these fluctuations and their temperature dependence have been obtained at the critical concentration of the liquid‐liquid immiscibility gap. These fluctuations are observed everywhere above the immiscibility gap.
A Dipole Model for the Outer Solvation Sphere and its Application to Outer Sphere Electron Transfer Reactions
Authors: Schmickler Wolfgang
Published: September 2012

The outer solvation sphere of an ion partaking in an outer sphere electron transfer reaction is viewed as an ensemble of polarizable dipoles. The formalism of Mandel and Mazur is used to derive expressions for the generating function and the energy of reorganization in terms of averages over molecular quantities. On passing to the continuum representation the results are shown to be equivalent to the theories of Marcus and Hush. The relation of the present work to the polaron model and to the work of Bockris and Sen are also discussed.
The Association of 3‐ethylpentanol‐3 in Carbon Tetrachloride from the Static Dielectric Permittivity and the Infrared Absorbance
Authors: Kunst M. , van Duijn D. , Bordewijk P.
Published: September 2012

Static dielectric constants and Infrared absorbances in the hydroxyl stretching range have been determined for solutions of 3‐ethylpentanol‐3 in carbon tetrachloride with molar fractions between 0.001 and 0.1 at temperatures between 15°C and 45°C.

The measurements favour the interpretation of the association of this alcohol by a monomer‐dimer‐tetramer equilibrium with heats of association of dimer and tetramer of 20 and 65 kJ/mol respectively. It appears that in a restricted concentration range this model is applicable to measurements of other alcohols in apolar solvents in the literature, and the model was used to calculate equilibrium constants and heats of association of these alcohols.
The Free Energy of Formation of Nickel Oxide
Authors: Berglund S.
Published: September 2012

The free energy of formation of NiO has been determined by an EMF method. The temperature range 825–1675 K was covered in a continuous series of observations. The results can be expressed as

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Reaktionen von Molekülen in definierten Schwingungszuständen (III), die Reaktion von HCl(ν) mit H‐, D‐, Cl‐ und Br‐Atomen
Authors: Arnoldi D. , Wolfrum J.
Published: September 2012

Der Einfluß einer selektiven Schwingungsanregung auf den Ablauf einfacher neutraler und endoenergetischer Reaktionen in der Gasphase wurde anhand der Reaktionen von HCl(ν) mit H‐, D‐, Cl‐ und Br‐Atomen mit Hilfe der Methode der laserinduzierten Fluoreszenz in einer Strömungsanordnung untersucht. Durch die Bestimmung der absoluten Konzentration der schwingungsangeregten Moleküle, die zeit‐aufgelöste Beobachtung der Atomkonzentration und den massenspektrometrischen Nachweis der Produkte der laserinduzierten Reaktionen über ein Molekularstrahl‐Probenahmesystem war eine direkte Unterscheidung zwischen reaktiven und energieübertragenden Prozessen möglich.

Bei einer Laserimpulsenergie von 10 mJ ergibt sich aus dem Vergleich der Intensität der Infrarotfluoreszenz der Zustände HCl(ν = 2) und HCl(r = 1) ein Anregungsgrad von

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Dieses Ergebnis erhält man auch aus der Messung des Temperaturanstieges von ΔT = 7 K in der Reaktionsmischung nach vollständiger Schwingungsrelaxation von HCl(ν) durch Chloratome.

Die Messungen der spezifischen Geschwindigkeitskonstanten k(ν = 1) wurden bei sehr geringem Anregungsgrad ausgeführt. Hierdurch konnte eine Entvölkerung des Zustandes HCl(ν = 1) auf dem Weg über höhere Schwingungszustände vermieden werden. Im einzelnen wurden bei 295 K folgende Ergebnisse erhalten:

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Der drastische Anstieg der Geschwindigkeit der Reaktion (5) um einen Faktor 1011 nach Schwingungsanregung von HCl(ν) erlaubte eine isotopenselektive Reaktionsführung der Art

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Die gebildeten BrCl‐Moleküle zeigen eine Anreicherung auf 90% Br35Cl.
Rate Measurements for the Reaction H + Cl2 → HCl + Cl by Lyman‐α Fluorescence
Authors: Wagner H. Gg. , Welzbacher U. , Zellner R.
Published: September 2012

The rate of the reaction between hydrogen atoms and chlorine has been determined in a discharge‐flow system. By use of sensitive detection of H atoms by Lyman‐α resonance fluorescence the reaction could be studied at low initial H atom concentrations and unperturbed by interfering processes. From measurements in the temperature range T = 252–458 K the Arrhenius expression
Rate Constant for the Reaction of OH with N2O at 298 K
Authors: Biermann H. W. , Zetzsch C. , Stuhl F.
Published: September 2012

A value of k1 = (3.8 ± 1.2) · 10−17 cm3 molecule−1 s−1 for the rate constant of the reaction of OH radicals with N2O was determined at 298 K. For these experiments OH was generated by flash photolysing mixtures of H2O and N2O and was monitored by resonance absorption using a path length of 560 cm. The results are discussed with regard to the atmospheric residence time of N2O.
Messung des Virialkoeffizienten‐Isotopieeffekts von verschieden deuterierten Methylaminen zwischen 300 und 550 K
Authors: Adam G. , Schäfer Kl. , Schramm B.
Published: September 2012

Wir legen Messungen der Virialkoeffizienten‐Isotopieeffekte für drei verschieden deuterierte Methylamine im Temperaturbereich zwischen 300 und 550 K vor. Es gelang uns, die Isotopieeffekte durch einfache Annahmen über die Änderungen der Parameter des zwischen‐molekularen Potentials zu deuten.
The Problem of the Description of Non‐stoichiometric Complex Formation in Liquids in Terms of Thermodynamic Equilibrium Constants
Authors: Hertz H. G.
Published: September 2012

Applying the well‐known equations of thermodynamics and statistical thermodynamics it is shown under what conditions the terming “complex formation” may be used without accompanying definition of what is understood to be a complex. Generally, when a set of thermodynamic stability constants is given this means that the liquid is divided into various environments characterized by certain amounts of standard work and mass, and the configurational ranges of the entities which appear as complexes are only implicitely defined. As an alternative to the description of the structure of the liquid in terms of the thermodynamic language the description in terms of molecular distribution functions is briefly sketched.
Information on the Orientation Dependent Molecular Distribution Function from Nuclear Magnetic Relaxation Data
Authors: Hertz H. G.
Published: September 2012

A general relation is given which allows the experimental determination of as many parameters of the orientation dependent molecular distribution function as intermolecular nuclear magnetic relaxation rates can be measured involving different interaction partners in the molecular pair. Then the construction of simple model molecular pair distribution functions from model atomic pair distribution functions is described. Finally, a method is reported which offers a qualitative determination of the configurational range involved in a given thermodynamic stability constant.
Temperature‐Jump Experiments with a Binary Critical Mixture Near the Critical Temperature
Authors: Woermann D.
Published: September 2012

The time course of turbidity of critical isobutyric acid/water mixtures is measured after perturbing the internal equilibrium of the mixture by a small temperature jump (e.g. δT ≃ 0.05 K). The experiments are carried out as function of the temperature distance from the critical temperature (0.1 K < T – Tc < 0.6 K). A mechanism for the relaxation of turbidity change is proposed having a relaxation time of the order of ζ2 D−1 with ζ = ζ0ϵ−v and D = D0ϵ−v (ζ = correlation length of concentration fluctuations, D = mutual diffusion coefficient, v = 2/3, ϵ = (T* – Tc)/Tc, T* = T + δT/2). The experimental data are in qualitative agreement with the proposed mechanism.
Studies by the Electron Cyclotron Resonance (ECR) Technique. XI. Interactions of Thermal‐Energy Electrons with the Molecules ClF3 and C2ClF3
Authors: Christodoulides A. A. , Schumacher R. , Schindler R. N.
Published: September 2012

Utilizing the ECR technique, the electron scavenging properties have been investigated for the molecules ClF3 and C2ClF3 at thermal electron energies. The following rate constants ka for electron attachment at 20°C and activation energies Eact were obtained:

ClF3:ka = 3.6 · 10–10 cm3 · sec−1; Eact = 5.4 kJ · mol−1 C2ClF3:ka = 6.6 · 10−12 cm3 · sec−1; Eact = 5.0 kJ · mol−1.

The possible reaction paths for the electron capture processes are discussed.
Mechanism of the Reduction of Lead Ions in Aqueous Solution (a Pulse Radiolysis Study)
Authors: Breitenkamp M. , Henglein A. , Lilie J.
Published: September 2012

Pure lead is precipitated in the y‐irradiation of aqueous solutions of lead perchlorate or lead acetate containing also an organic solute for scavenging OH radicals. The yields in the presence of the radical scavenger are above 3 lead atoms/100 eV for formate and aliphatic alcohols and about 0.3 for cyclopentane and t‐butanol. Pulse radiolysis experiments showed that hydrated electrons and 1‐hydroxy alkyl radicals reduce Pb2+ to form Pb+, Pb+ can disproportionate to form Pb + Pb2+ Pb+ can also react with 1‐hydroxylalkyl radicals to form lead organic compounds that decompose to form Pb. The rate constants of these reactions were determined.

Pb2+ solutions were also pulse irradiated under a hydrogen pressure of 50 atm. H atoms did not reduce Pb2+ under our concentration conditions. They reacted with Pb+ to form the intermediate PbH+. Its spectrum was measured and the rate constant for its disappearance according to 2PbH+ → Pb2+ + Pb + H2 was determined.

The results are discussed in terms of the standard redox potentials of the systems Pb2+/Pb+ and Pb+/Pb in connection with the standard potentials of 1‐hydroxyalkyl radicals and hydrogen atoms. A comparison of the lead reduction is also made with the reduction of Ni2+ and Cd2+. The intermediates of the reduction in the presence of H atoms may also be present in the dissolution of metals in water under H2 production.
The Reaction of O(21D2) with Molecular Chlorine Studied by Atomic Absorption Spectroscopy in the Vacuum Ultra‐Violet
Authors: Fletcher I. S. , Husain D.
Published: September 2012

A kinetic study of electronically excited oxygen atoms, O(21 D2), in the presence of molecular chlorine is presented. The optically metastable atoms were generated by repetitive pulsed irradiation of ozone in the Hartley‐band continuum and monitored photoelectrically in absorption by time‐resolved attenuation of atomic resonance radiation in the vacuum ultra‐violet at δ = 115.2 nm (O(3D1D20) ← O(21D2)) using signal averaging techniques. The absolute second order rate constant for total quenching by Cl2 is found to be kCl2 = 2.2 ± 0.2 · 10−10 cm3 molecule−1 sec−2 (300 K). Using the value for kO3 derived from previous measurements employing this method, we find that kCl1/kO3 = 0.81 ± 0.05, in substantial agreement with the ratio derived recently by Freudenstein and Biedenkapp who used an indirect procedure involving a complex kinetic analysis. The absolute datum for kCT2, coupled with Freudenstein and Biedenkapp's observation, provides the basis for discussing the various pathways for reaction of O(21D2) + Cl2 using symmetry arguments for both the weak spin orbit coupling approximation and (J, Q) coupling, in order to discuss individual spin orbit states.
Elektronenspektren und Elektronenstruktur von Ethidiumbromid und verwandten Verbindungen 1. Mitteilung: Phenanthren, Phenanthridin und N‐Äthyl‐phenanthridinium‐bromid
Authors: Zimmermann Ingfried , Zimmermann Herbert W.
Published: September 2012

Die Absorptions‐, Emissions‐ und Polarisationsspektren von Phenanthren, Phenanthridin und N‐Äthyl‐phenanthridinium‐bromid wurden gemessen und in semiempirischer SCF‐CI‐PPP‐Näherung berechnet. Die Klassifizierung der Spektren anhand des Perimetermodells ergab, daß die intensivste Absorptionsbande des Phenanthrens und Phenanthridins – entgegen älteren Zuordnungen – als Überlagerung von 1Ba und 1Bb aufzufassen ist.
Kernresonanz‐Untersuchungen zur Diffusion der Kationen in Li2O
Authors: Oei Y. S. , Richtering H.
Published: September 2012

An 7Li in Li2O wird die Spin‐Gitter‐Relaxationszeit bei verschiedenen Larmor‐Frequenzen und bei Temperaturen bis 780°C bestimmt. In reinem Li2O überwiegt die Dipol‐Dipol‐Wechselwirkung. Das zugehörige Relaxationsmaximum wird, je nach Larmor‐Frequenz, bei 600–750°C gefunden. Für die mittlere Sprungfrequenz der Li+ ‐Ionen ergibt sich im Bereich der Eigenfehlordnung (600–780°C)

v(Li) = 2,5 · 1013 exp (11 ± 0,05)eV)/kT )sec−1.

Bei Dotierung mit MgO und LiF werden zwei verschiedene Gitterfehler erzeugt, deren Platzwechsel zu je einem zweiten Relaxations‐maximum führt. Diese Maxima können durch eine Quadrupol‐Wechselwirkung erklärt werden; sie liegen bei tieferen Temperaturen als das Dipol‐Dipol‐Maximum. Durch beide Fehlstellen wird die mittlere Sprungfrequenz der Li+‐Ionen erhöht, es handelt sich danach um Kationen‐Leerstellen und Kationen auf Zwischengitterplätzen. Die zugehörigen Schwellenenergien betragen (0,55 ± 0,05) und (0,3 ± 0,05) eV. Dotierung mit LiOH führt wie bei MgO zu Kationen‐Leerstellen, die Löslichkeit ist aber nur klein. Aus den Ergebnissen kann auf Frenkel‐Fehlordnung in Li2O geschlossen werden, für die Fehlordnungsenergie ergibt sich (1,3 ± 0,2) eV.
Margulis‐Effekt durch Änderung der Oberflächenverteilung
Authors: Bradaczek Hans
Published: September 2012

Es wurde die noch ungeklärte Frage nach der Abnahme der Lösungsgeschwindigkeit bei Lösungsversuchen an Arsentrioxid (Margulis‐Effekt) durch Vermessung der Teilchenoberfläche als Abnahme der spez. Oberfläche der Teilchen mit zunehmender Lösungszeit nachgewiesen.
Fundamental Limitations in the Computational Process
Authors: Landauer Rolf
Published: September 2012

Information in computers, in biological systems, or in any other form, inevitably requires the use of physical degrees of freedom. Information is not a purely mathematical or philosophical entity. It is subjected to physical restrictions and these are reviewed to the extent they are now understood. The discussion of memory is brief since this area is well documented in earlier reviews. Logic and switching processes are analyzed in more detail. Bennett's thesis that computing can be a completely reversible process, both logically and physically, with arbitrarily small energy dissipation, is demonstrated. The model used for this discussion is a Turing machine modelled, in general, on Bennett's work, but using the Fredkin gate as the basic device for interaction between information streams. Reversible computers can simulate evolutionary behavior and related games just as it is done today on practical computers. We can thus have a form of self‐organizing activity among the bit patterns, with very little energy expenditure. A brief discussion of systems which hold information with the aid of continual energy dissipation is also given. In multi‐stable systems of this sort the evaluation of relative stability between different states of local stability cannot be done by simply comparing the neighborhood of the states involved, but must include consideration of the detailed kinetics along the improbable intervening transition paths. As a consequence it is suggested that theories of biological evolution must consider the detailed kinetics along the paths of evolution. This cannot be avoided by thermodynamic or information‐theoretic shortcuts which only compare initial and final states.