The isotopes259106,260106, and261106

In irradiations of²⁰⁷Pb and²⁰⁸Pb, respectively, with⁵⁴Cr theα-decay of the isotopes²⁵⁹106,²⁶⁰106, and²⁶¹106 could be observed for the first time. For²⁶⁰106 a spontaneous fission branch of (50 _?20 ⁺³⁰ )% was observed. The isotopes were identified by genetic relationships of α-decay after separation in-flight with the velocity filter SHIP and implantation into a position-sensitive silicon surface-barrier detector. The measured partial fission halflife of the doubly even isotope²⁶⁰106 of (7.2 _?2.7 ^+4.8 )ms exceeds the predicted values by at least a factor of 40. This result could be explained by the high shell corrections of the ground state mass, derived from the measured α-decay energies. The experimental results show evidence for an island of purely shell stabilized nuclei in the region of deformed isotopes beyond the actinides.     

Valence state and magnetic interactions in magnetically ordered Eu(Pd1−x Au x )2Si2

X-ray diffraction,¹⁵¹Eu Mössbauer effect (ME) and magnetic susceptibility measurements have been performed to investigate the valence behavior and the magnetic interactions of the Eu ions in the intermetallic series Eu(Pd_1–x Au _x )₂Si₂ (0x1) as a Forx>0.4 all experimental techniques are in agreement with each other and suggest a divalent 4f ⁷ ground state of the Eu ion. Belowx=0.4 the different methods lead to different results: while the lattice parameters and the ME isomer shift suggest an instable behavior of the valence the magnetic susceptibility proves a pure divalent 4f ⁷ ground state. These differences can be explained by assuming a partial extension of the 4f-shell radius such that the localized character of the 4f-electrons is preserved.Dedicated to B. Mühlschlegel on the occasion of his 60th birthday     

Hall effect of noncrystalline Zr−Cu films

Quench condensed Zr _x Cu_1–x films offer a wide concentration range (0.1x0.9) for measurements of the Hall coefficientR _H of amorphous Zr–Cu alloys.R _H changes sign as a function of composition, from negative to positive, as the Zr concentration is increased. The sign change is observed in a narrow concentration range at aboutx=0.22, without any peculiarity of the conductivity at this crossover concentration. The Hall coefficient of the unannealed Zr-rich films is nearly independent of temperature. However, both, the values ofR _H and of the temperature dependence ofR _H change with a heat treatment well below the crystallization temperature. This is most obvious for the films with a composition close to the cross-over concentration.Dedicated to B. Mühlschlegel on the occasion of his 60th birthday     

Electron correlations in hydrocarbon molecules

An extensive investigation is made of electron correlations in the ground state of hydrocarbon molecules. This is done by starting from a semiempirical self-consistent field (SCF) calculation. The interatomic correlations are studied by means of a previously developed local approach to the correlation problem. It is demonstrated that the various contributions to the interatomic correlation energy can be described by simple analytical expressions which depend on the type of bond as well as on the bond lengths and angles. The results are easily understood in physical terms. The intraatomic correlations are obtained from an atoms in molecules type of approach as elaborated by Lievin et al. It makes use of a population analysis of the ground-state wave function as well as of calculations for the C and H atoms. We have then a very simple, and as it turns out rather accurate calculational scheme at hand. The computational times involved are of the same order as those for the fast SCF programs. As an application of the theory we have calculated the correlation energy difference between naphthalene and azulene.Dedicated to B. Mühlschlegel on the occasion of his 60th birthday     

Synthesen von α,β-ungesättigten 2-(2-Oxo-benzazolin-3-yl)-3-hydroxy-dithio-carbonsäure-alkylestern und entsprechend substituierten Keten-S,S-acetalen sowie deren Kristall- und Molekülstruktur

Summary The new alkyl 2-(2-oxo-benzazoline-3-yl)-3-hydroxy dithiocrotonates and dithiocinnamates4 and the corresponding ketene dithioacetals2 and5 are obtained by dithiocarboxylation of the 3-acceptormethyl substituted benzazoline-2-ones1 or3. Alkylation at room temperature gives compounds4 whereas at higher alkylation temperature2 or5 are formed. The results of X-ray analyses performed for methyl 3-hydroxy-p-chloro-dithiocinnamate4d and of N-[1-(4-chloro-benzoyl)-2,2-bis(methylthio)-vinyl]-benzothiazoline-2-one5e are discussed.

     

The role of small silver clusters in photography

Size-selected silver cluster ions have been produced in a mass spectrometer arrangement and have been deposited onto binder-free AgBr microcrystals. Clusters containing less than four silver atoms did not catalyze development (reduction) of the microcrystals. However, application of clusters containing four or more silver atoms rendered the crystals immediately developable in a conventional photographic developer. This for the first time proves directly, that a so-called latent image speck under these conditions of development requires a minimum number of four silver atoms.