Vergleichende SIMS- und AES-Tiefenprofil-Analysen an einem Ni/Cr-Vielschicht-System

Ohne Zusammenfassung

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Comparison of SIMS and AES depth profile analyses of a Ni/Cr multilayer system

     

α-particle break-up in the interaction with protons at 8.6 GeV/c 4He momentum

Helium break-up reactions have been studied in ⁴He-proton interactions at 8.6 GeV/c⁴He momentum in the hydrogen bubble chamber. Total and differential cross sections for different reaction channels without pion production have been measured. The results have been compared with multiple scattering model predictions.     

Untersuchungen zur Korrosion durch Kunststoffschmelzen an verschiedenen w?rmebehandelten Werkzeugst?hlen mittels ESCA, AES und SIMS

Summary The processing of synthetic material by injection molding machines and extruders produce wear on metal surfaces being in contact with the synthetic material. The corrosion in the melting areas of such machines depends on the chemical and morphological properties of the steel surface. The processing generates chemical changes which can be monitored by means of surface analysis methods. We examined different steels — containing Cr, Mo and V — which were corroded by various melts of synthetic materials. AES, ESCA and SIMS measurements show that some components especially chromium, play a key role for the corrosion process. Corrosion at the surface causes changes of the chemical composition along varying depths (100 – 300 Å). The knowledge of the correlation between chemical changes and surface properties will be helpful for choosing adequate alloys for synthetic material processing machines.     

Exact solution of a general two-dimensional Ising model: The partition function

The exact partition function per spin is obtained for a two-dimensional generalization of the Ising model. This general model consists of a unitary cell that is repeated throughout the system. The unitary cell is made up of spins in t columns and q rows with arbitrary energies between them. The exact result is given in terms of certain Ψ quantities (see section 2), which can be determined for particular cases.

It is always possible to transform the unit cell in order to obtain a desired given model. Thus, the results for several known models are recovered, e.g., the Utiyama and the hexagonal (with three different interaction parameters) models. Furthermore, explicit results are presented for other models hitherto not reported in the literature, as are the general hexagonal (with six different interaction parameters), the general triangular model (with six different interaction parameters) and the tetragonal-triangular (with seven different interaction parameters) models.     

Investigation of the excimer dynamics in 9,10-dichloroanthracene crystals using picosecond spectroscopy

The dynamics of excimer formation, excimer migration, and excimer dissociation in β-9,10-dichloroanthracene crystals were investigated by means of picosecond time-resolved fluorescence spectroscopy. In the temperature range from T = 20 K to T = 40 K we were able to temporally resolve the relaxation into the excimer state. The excimer formation rates were determined to be k ≈ 1.8 × 10¹¹ s^?1 at T = 40 K and k ≈ 2.0 × 10¹⁰ s^?1 at T<30 K. The excimer migration was investigated by measuring the excimer annihilation rate as a function of temperature. At room temperature 20% of the excimers are dissociated. The excimer binding energy is estimated to be B = 1360 cm^?1. The experimental results are explained in terms of a kinetic scheme comprising the population and depopulation of exciton, trap, and excimer states. The nature of the trap state is identified and it is shown that thermal activation of a 25 cm^?1 librational mode induces the relaxation of the trap into the excimer state.