Measurements of angular distributions of sputtered material as a new tool for surface-segregation studies: Segregation in CuPt alloys

The angular distribution of copper and platinum sputtered by argon ions from polycrystalline CuPt targets at 77 K has been measured by a collection technique. The argon-ion energy has been varied from 1.25 to 320 keV. For bombardment energies above 20 keV, differences in the angular distributions for the two elements indicate a strong copper segregation to the surface during bombardment.     

The differential equations of the Voigt function

The three second-order partial differential equations of the Voigt function are presented, leading to a powerful and accurate method of determining the Voigt function in the calculation of a line profile in a stellar atmosphere.     

Stopping power in insulators and metals without charge exchange

The slowing-down process of pointlike charged particles in matter has been investigated by measuring the stopping power for antiprotons in materials of qualitatively very different nature. Whereas the velocity-proportional stopping power observed for metal-like targets such as aluminum over a wide energy range of 1-50 keV is in agreement with expectations, it is surprising that the same velocity dependence is seen for a large band-gap insulator such as LiF. The validity of these observations is supported by several measurements with protons and several checks of the target properties. The observations call for both a qualitative explanation and a quantitative theoretical model.     

Mott transition and suppression of orbital fluctuations in orthorhombic 3d1 perovskites

Using t(2g) Wannier functions, a low-energy Hamiltonian is derived for orthorhombic 3d(1) transition-metal oxides. Electronic correlations are treated with a new implementation of dynamical mean-field theory for noncubic systems. Good agreement with photoemission data is obtained. The interplay of correlation effects and cation covalency (GdFeO3-type distortions) is found to suppress orbital fluctuations in LaTiO3 and even more in YTiO3, and to favor the transition to the insulating state.     

Wasserverbrückte nickelorganoverbindung: Kristall- und molekülstruktur von bis(2,2′-bipyridin-2-methyl-pent-2-enal-nickel) · H2O [(bipy)Ni(C2H5ChC(CH3)CHO)]2 · H2O

The structure of the dimeric complex [(bipy)Ni(MEA)]₂ · H₂O (MEA = 2-methylpent-2-enal (α-methyl-β-ethylacrolein)) was determined by X-ray structural analysis (space group P$\text{1}$, a 10.843(4), b 9.650(3), c 17.116(2) Å, Z = 4, R = 0.05). The MEA ligand is not exclusively coordinated through the olefinic group, but there is however, interaction with the C atom of the neighbouring CO group (NiC distances 2.28 and 2.40 Å in both symmetrically independent molecules). The true bonding situation can be described as in between purely olefinic and purely π-allylic. Two molecules of (bipy)Ni(MEA) are connected by a molecule of water, which bonds asymmetrically to the two oxygen atoms of both aldehyde groups. The compound described is apparently the first example of an organonickel compound with bound water. The compound's importance for complex catalysed aldol condensations is discussed.