Metal clusters on an inert surface: a simple model

The shapes of metal clusters (with 2 to 14 valence electrons) on an inert surface are studied with a simple model based on the ultimate jellium model. It is shown that within certain approximations the surface-cluster interaction can be described with an external potential in the Kohn-Sham method. No restrictions for the cluster geometry are imposed. The results show that depending on the strength of the interaction and on the size of the cluster, the ground state is either planar or three-dimensional, but in many cases both geometries are stable and there is a marked energy barrier between them. The results agree qualitatively with ab initio calculations of Na clusters on a NaCl(100) surface.     

Application of fast solvent extraction processes to studies of exotic nuclides

The nucleus²³Na has been investigated by studying the primary γ-rays emitted from 53 keV neutron capture in it using a high resolution and high efficiency (100%) HPGe detector and NaI(T1) detector for anti-Compton. 24 primary γ-rays were placed in the²⁴Na, in which 3 primary γ-rays were new ones from a (n, γ) reaction, and reported for the first time. In order to obtain an exact energy calibration within 7 MeV,⁵⁶Fe(n,γ)⁵⁷Fe reaction was used at thermal neutron energy. Intensity calibration was obtained from the²⁷Al(p,γ)²⁸Si reaction atE _p=2046 keV. The neutron binding energy of²⁴Na was determined to be 6959.75 keV.     

First order magnetic transition,magnetic structure,and vacancy distribution in Fe2P

The para- to ferromagnetic transition in Fe₂P has been studied using Mössbauer spectroscopy. The magnetic hyperfine fields drop abruptly from about half of their saturation values to zero at 214.5 K indicating a first order transition. The isomer shifts show a discontinuous change at the transition point. For some samples the transition takes place over a wide temperature range, probably due to impurities and other imperfections in the samples. From the magnetic hyperfine fields at 15 K the magnetic moments can be deduced to be 1.14 μ_B and 1.78 μ_B for Fe(1) and Fe(2), respectively. An assignment of the components in the Mössbauer spectra to the two crystallographically nonequivalent iron positions has been made from the temperature variation of the spectra.The ordering of metal vacancies has been investigated by a Mössbauer study of a nonstoichiometric Fe₂P sample and by an X-ray diffraction study of a nonstoichiometric Mn₂P crystal.     

Photoelectric evidence for a neutral excited state in fully polymerized polydiacetylene-p-(toluenesulfonate) single crystals

The intensity dependence of photocurrent transients excited by the 1.06 μ line of a Nd laser has been measured. Observation of an I² and an I³ branch indicate that charge carriers can be generated via two-quantum absorption and that at high intensities photoionization of a neutral excited state with a lifetime of the order 10^?10 s dominates.     

Zur Kinetik der Spinellbildung von β-Ga2O3 mit zweiwertigen Oxiden. IV. Reaktionen 2. Art im System CoO-β-Ga2O3

The solid-state reaction of the second kind in a sandwich type diffusion couple of $\text{Co}{}_{\mathrm{1?z}}\text{Ga}{}_{\mathrm{<mtext>2z</mtext><mtext>3</mtext>}}\text{O}$ and β-Ga₂O₃ has been investigated between 1249 and 1550°C in air. The quantity z, which corresponds to the saturation concentration of β-Ga₂O₃ in CoO, was determined as a function of temperature by X-ray methods and the optical microscope; the homogeneity range of the spinel phase $\text{Co}{}_{\mathrm{1?y}}\text{Ga}{}_{\mathrm{<mtext>2+</mtext><mtext>2y</mtext><mtext>3</mtext>}}\text{O}{}_4$ was investigated also. The growth of the thickness of the reaction layer follows a parabolic rate law; the activation energy is 71.6 kcal/mole. A comparison of reaction rate constants of the first and second kind in connection with experimental results, achieved with a modified marker technique, leads to confirmation of the Wagner mechanism for the formation of CoGa₂O₄ spinel as supposed before by Laqua. Reaction rate constants of the second kind, calculated from interdiffusion profiles in CoO-β-Ga₂O₃ diffusion couples, are in good agreement with experimental values. Presented data are used for estimating interdiffusion coefficients for the CoO-β-Ga₂O₃ system according to theoretical aspects developed by Pelton, Schmalzried, and Greskovich.     

Thermodynamics of the Laminar Donnan System

Thermodynamic quantities of a polyelectroyte immersed in salt solution are derived modeling the polyelectrolyte by a sequence of charged parallel flat plates. The starting point for the analysis is the derivation of the Gibbs free enthalpy in its canonic variables pressure (p) and temperature (T), i.e., as a thermodynamic potential. From this, further thermodynamic quantities such as Helmoltz free energy, entropy, internal energy, compressibility, isobar and isochor heat capacities, and expansive force are derived in analytical expressions by differentiation. All these formulas contain the parameter plate surface charge density (sigma) that provides a measure of the discontinuity of the polymer charge distribution that can be used to fit the theory to experimental data. Thermodynamic quantities are also known from the classical Donnan equilibrium that treats the polyelectroyte charge network as a charge continuum. A limiting process is used to perform the transition from the laminar Poisson- Boltzmann model to the continuous Donnan equilibrium. In general, the expressions of the Donnan system are recovered for plate charge density sigma-->0, number of plates Z-->infinity, and sigma Z=constant. Copyright 2000 Academic Press.     

New photochromic 2H-1.4-oxazines and spiro-2H-1.4-oxazines

The synthesis and the photochemical behaviour of 4 new 2H-1.4-oxazines and 3 new spiro-2H-1.4-oxazines is described.     

1.5-Diaza-3.7-diphospha-cyclooctane

The alkyl (aryl)-bishydroxymethylphosphines react with primary amines to give the title compounds. With optically active amines optically active phosphines are formed.     

Über die Umsetzung von 2-Methyl-2,5-diphenyl-imidazolin-4-thion und 2-Methyl-2,5-diphenyl-4-chlor-2H-imidazol mit aliphatischen und aromatischen Aminen,Alkoholen und Phenolen

Zusammenfassung Aliphatische Amine bzw. Alkohole reagiren (in Gegenwart von PbO) mit 2-Methyl-2,5-diphenyl-imidazolin-4-thion (1) glatt zu 4-Alkylamino-2H-imidazolen (2 a-f, 7) bzw. 4-Alkoxy-2H-imidazolen (9 a-g). Die Darstellung von 4-Arylamino-2H-imidazolen (4 a-j) bzw. 4-Aroxy-2H-imidazolen (10 a-t) gelingt in guten Ausbeuten durch Umsetzung von 2-Methyl-2,5-diphenyl-4-chlor-2H-imidazol (3) mit aromatischen Aminen in siedenden Lösungsmitteln (Petroläther, Aceton) bzw. mit Phenolen in siedendem Aceton in Gegenwart von HCl-Acceptoren (K₂CO₃, Dabco). Die Umsetzung von3 mit Anthranilsäure liefert in 83proz. Ausbeute 1-Methyl-1,3-diphenyl-1H, 9H-imidazo[5,1-b]chinazolin-9-on (6). Aus3 und Thiophenol erhält man glatt 2-Methyl-2,5-diphenyl-4-phenylthio-2H-imidazol (11).

---

On the reaction of 2-Methyl-2,5-diphenyl-imidazoline-4-thione and 2-Methyl-2,5-diphenyl-4-chloro-2H-imidazole with aliphatic and aromatic amines, alcohols and phenols (joint action of elemental sulfur and gaseous ammonia upon ketones, LXXVI

Aliphatic amines and alcohols (in the presence of PbO) easily react with 2-methyl-2.5-diphenyl-imidazoline-4-thione (1) to 4-alkylamino-2H-imidazoles (2 a-f, 7) and 4-alkoxy-2H-imidazoles (9 a-g), resp. 4-arylamino-2H-imidazoles (4 a-j) are prepared in good yields by the reaction of 2-methyl-2.5-diphenyl-4-chloro-2H-imidazole (3) with aromatic amines under reflux in light naphtha or acetone; in the same manner 4-aroxy-2H-imidazoles (10 a-t) are obtained from3 and phenols in boiling acetone in the presence of HCl-acceptors (K₂CO₃, Dabco). Reaction of3 with anthranilic acid leads to1-methyl-1.3-diphenyl-1H.9H-imidazo[5.1-b]chinazoline-9-one (6) in 83% yield. By reaction of thiophenol with3 2-methyl-2.5-diphenyl-4-phenylthio-2H-imidazole (11) is easily obtained.

---

---

Herrn Prof. Dipl.-Ing., Dr. techn., Dr. e. h.Otto Kratky zum 70. Geburtstag herzlichst gewidmet.

---

Teil der DiplomarbeitJ. Gräber, Techn. Hochschule Aachen, 1970.

---

Teil der DiplomarbeitU. Lames, Techn. Hochschule Aachen, 1971.