Preparation of protected photoinitiator nanodepots by the miniemulsion process

The solid photoinitiator Lucirin TPO was encapsulated within a polymer shell by using the miniemulsion process. A solution of Lucirin TPO in methyl methacrylate (MMA) or butyl acrylate (BA)/MMA mixture was miniemulsified in water followed by a polymerization process in which phase separation of the Lucirin TPO and the formed polymer led to amorphously solidified Lucirin TPO nanoparticles encapsulated by polymer. These nanocapsules were freeze-dried and could be redispersed in acidic monomers, which are applied in polymeric dental adhesives. It is shown by ¹H nuclear magnetic resonance spectroscopy that the shell separates the Lucirin TPO, which is sensitive to degradation in acidic media, from an ambient acidic monomer phase and protects it from fast decomposition. Investigations of the release kinetics of Lucirin TPO from the nanocapsules reveal that the kinetics are strongly dependent on the composition of the surrounding continuous phase.     

Observation of molecules produced from a Bose-Einstein condensate

Molecules are created from a Bose-Einstein condensate of atomic 87Rb using a Feshbach resonance. A Stern-Gerlach field is applied, in order to spatially separate the molecules from the remaining atoms. For detection, the molecules are converted back into atoms, again using the Feshbach resonance. The measured position of the molecules yields their magnetic moment. This quantity strongly depends on the magnetic field, thus revealing an avoided crossing of two bound states at a field value slightly below the Feshbach resonance. This avoided crossing is exploited to trap the molecules in one dimension.     

Nucleation and growth of molecular organic crystals in a liquid film under vapor deposition

We report on the nucleation and growth of tetracene in a thin liquid film which is continuously supersaturated by vapor deposition of molecules onto the film. In a first stage, nucleation and fast anisotropic two-dimensional dendritic growth occurs. In a second stage, the dendrites coarsen into pallet-shaped crystals. These are highly oriented with respect to the plane of the liquid film and reach a lateral size of several 100 microm. The two-dimensional growth mode is explained by the confined growth geometry in the liquid in combination with the anisotropy of the crystal structure.     

Die Klassifikation nach inneren Symmetrien beim quantenmechanischen Mehrkörperproblem

For systems ofn identical particles with harmonic two-body interaction a method is derived which allows for anyn the construction of a complete orthonormal set of functions that are translationally invariant and are classified according to energy, permutational symmetry,SU (3), angular momentum, and parity. Moshinsky's method for the determination of translationally invariant states with definite permutational symmetry for harmonic two-body interaction is briefly reviewed and is extended to additionalSU (3)-classification. His method, however, is seen to be restricted to the casesn=3,n=4.     

Measurement of the dipole and electric quadrupole strength distributions up to 10 MeV in the doubly magic nuclei 40Ca and 48Ca

We have made the first detailed measurements of a diffusive supersonic radiation wave in the laboratory. A 10 mg/cm(3) SiO2 foam is radiatively heated by the x-ray flux from a laser-irradiated hohlraum. The resulting radiation wave propagates axially through the optically thick foam and is measured via time-resolved x-ray imaging as it breaks out the far end. The data show that the radiation wave breaks out at the center prior to breaking out at the edges, indicating a significant curvature in the radiation front. This curvature is primarily due to energy loss into the walls surrounding the foam.