Anharmonic corrections in unimolecular theory: a monte carlo approach

The effects of anharmonicity on the integrated state densities required by RRKM formulations are examined. A PitzerGwinn-like approximation is developed in which the desired state densities are related to those for a solvable reference system by an energy-dependent, classical correction factor. A Monte Carlo calculation procedure is outlined.     

Dynamical aspects of precursor state kinetics

An examination of precursor adsorbed states from a dynamical viewpoint reveals that two commonly used models of precursor kinetics are not generally applicable. For the case of molecular chemisorption, simple, linear rate laws may not be valid unless the adsorbate-solid system meets certain dynamical criteria. On the other hand, for dissociatively chemisorbed species, a serious error can be made in estimating the effect of temperature on the adsorbate dissociation rate if one ignores, as is usually done, the temperature dependence of the initial sticking probability of the molecule.     

Semiclassical theory of atom/solid surface collisions; Solution of steele's model

Steele's model of elastic gas/surface scattering is solved semiclassically. The model is reasonably successful in reproducing the diffractive data of Smith, O'Keefe, Saltsburg and Palmer.     

Synthesis of Tetraarylethene Luminogens by C−H Vinylation of Aromatic Compounds with Triazenes

Tetraarylethenes are obtained by acid‐induced coupling of vinyl triazenes with aromatic compounds. This new C?H activation route for the synthesis of aggregation‐induced emission luminogens is simple, fast, and versatile. It allows the direct grafting of triarylethenyl groups onto a variety of aromatic compounds, including heterocycles, supramolecular hosts, biologically relevant molecules, and commercial polymers.     

Kneelike structure in the spectrum of the heavy component of cosmic rays observed with KASCADE-Grande

We report the observation of a steepening in the cosmic ray energy spectrum of heavy primary particles at about 8×10(16) eV. This structure is also seen in the all-particle energy spectrum, but is less significant. Whereas the "knee" of the cosmic ray spectrum at 3-5×10(15) eV was assigned to light primary masses by the KASCADE experiment, the new structure found by the KASCADE-Grande experiment is caused by heavy primaries. The result is obtained by independent measurements of the charged particle and muon components of the secondary particles of extensive air showers in the primary energy range of 10(16) to 10(18) eV. The data are analyzed on a single-event basis taking into account also the correlation of the two observables.     

Nanopowders of ferroic oxides for magnetoelectric composites

Piezoelectric oxides are currently being considered in combination with magnetic materials for the development of magnetoelectric composites, in which stress transfer across the interface is a key issue. In this context, we report here a detailed study of the mechanochemical activation processes of the ferroelectric perovskite BiScO₃–PbTiO₃ and of the ferrimagnetic spinel NiFe₂O₄. Highly sinterable, single-phase nanopowders of both ferroic oxides are synthesised, and used for the preparation of high-density materials and two-phase composites by hot pressing. Emphasis is put on studying chemical reactions at and interdiffusion across the interface between the two phases using high spatial resolution techniques such as micro X-ray diffraction and piezoresponse force microscopy. The feasibility of preparing magnetoelectric composites by this approach is demonstrated, for which the necessity of controlling physicochemical processes at the interface is key to obtain functionality.