Potentiometrische p-Bestimmung

Ohne Zusammenfassung     

Improved limits on double beta processes in 92Mo

New limits on double beta processes in ⁹²Mo have been obtained using a 400 cm³ HPGe detector and an external source of high-purity natural molybdenum. At confidence level CL= 90% they are 1.9 · 10²⁰ y for the (0v + 2v)β⁺EC transition to the ground state, 8.9 · 10²⁰ y and 8.1 · 10²⁰ y for the (0v + 2v)ECEC transitions to first excited 2 ₁ ⁺ and 0 ₁ ⁺ states in ⁹²Zr, correspondingly.     

On the non-existence of homoclinic orbits for a class of infinite dimensional Hamiltonian systems

We prove that for a class of infinite dimensional Hamiltonian systems certain homoclinic connections to the origin cease to exist when the non-linearities have `super-critical' growth. The proof is based on a variational principle and a Poho\v{z}aev type identity.

     

Thermally stimulated creep study of bismaleimide/carbon fiber composite

The correlation between structure/microstructure and thermomechanical properties has been investigated by the Thermally Stimulated Creep (TSC) technique in a high performance thermostable thermoset matrix composite. The high resolving power of this technique allows us to analyse the retardation mode. The kinetics of molecular movements liberated at the glass transition has been investigated by the technique of fractional loading: the analysis of each elementary process gives the real compliance and the retardation time as a function of temperature. The values of the activation parameters show the existence of a compensation phenomenon which characterizes the microstructure. It also gives access to the loss compliance of the composite material as a function of temperature and frequency. The predictive calculation of loss compliance has been validated by the results obtained by dynamic mechanical analysis (DMA).     

Raman scattering in amorphous films of In1−xSex alloys

Raman scattering (RS) in amorphous films of In_1−xSe_x with 0.67±x?0.38 has been studied in backscattering geometry with the use of a microscope. Recorded RS spectra are revealing a mixed vibrational density-of-states and molecular character. The spectra spread from the Rayleigh line up to 200-250 cm⁻¹. The bands superimposed on the continua are related to zone center modes of the relevant crystal counterpart, Se-Se or In-In vibrations. The RS spectra suggest the structure of the In_1−xSe_x alloys to be the continuous random network built up of In centered tetrahedral clusters with In and Se atoms at the corners. The structure of the Se-rich alloys is similar to 4-2 networks with dominant InSe_4/2 clusters and two-fold coordination of Se bridging atoms. That of the In-rich alloys is expected to resemble 4-3 network with rather strong involvement of In atoms at corner of the In-centered tetrahedral clusters and Se atoms being linked to three In ones.     

Interface and material characterization of thin Al2O3 layers deposited by ALD using TMA/H2O

Thin Al₂O₃ layers were grown by atomic layer deposition using trimethylaluminum (TMA) and water as precursors on 1.2 nm thermal SiO₂ and HF cleaned Si surfaces. The stoichiometry and the contamination (H, OH and C) of as-deposited and N₂ annealed thick Al₂O₃ layers were characterized by secondary ion mass spectrometry (SIMS), elastic recoil detection analysis (ERDA) and X-ray photoelectron spectroscopy (XPS). We show a perturbed region (≈5 nm thick) at the Al₂O₃/Si interface by XPS and Auger electron spectrometry (AES). Post-deposition annealings induced important interface oxidation, Si atoms injection and SiO₂/Al₂O₃ mixture whereas the initial interface was abrupt. Silicon oxidation before Al₂O₃ growth highly limits interfacial oxidation and improves interfacial quality. We proposed that OH groups may play a key role to explain silicon oxidation during post-deposition annealings in inert ambience with low oxygen contamination levels.     

Coulomb excitation of230Th with32S,84Kr and142Nd projectiles

The Coulomb excitation measurements for the²³⁰Th nucleus with³²S,⁸⁴Kr and¹⁴²Nd projectiles are presented. The use of different projectiles allowed us to get information in the ground-state band and side bands. The energy spectrum of the ground-state band and of the lowest negative-parity band have been investigated up to the spin valueI=24⁺ andI=19^?(21), respectively. Five side bands (K ^π=0⁺, 2 ₁ ⁺ , 2 ₂ ⁺ , 1^?, 2^?) were observed also. The branching ratios for a large number of transitions in the spin regionI≦10 for π=+1 andI≦9 for π=? 1 are analysed. The full set of experimental data contains information on the mixing of the adiabatic states and on the nuclear response to the electromagnetic field ofγ-radiation. It is shown that the experimental data may be explained taking into account the coupling of the ground-β- and twoγ-bands and also of theK ^π=0^?, 1^? and 2^? negative-parity bands. An enhancement of the transitions from theγ-to theβ-band in respect to the transitions from theγ to the ground band and from theβ- to the ground band is reported. The mixing of the negative-parity bands is found to be typical for the alignment of the octupole-vibrational angular momentum. The strong spin dependence of the intrinsic matrix elements of the electric-dipole operator follows from the branching ratios of inter- and intra-band transitions from theK ^π=0^? states.