Shape transitions and shape coexistence in the Ru and Hg chains

The General Collective Model (GCM) is revised and applied to the chain of^182–196Hg- and^96–108Ru-isotopes. Calculated energy spectra, absolute B(E2) values and Quadrupole moments are presented and compared to experiment. For many of these nuclei a coexistence of spherical and triaxial shapes was found. Additionally we investigated the shape transition within the Ru-chain from prolate (⁹⁶Ru) over spherical (⁹⁸Ru) to triaxial (A ≧100). The results are compared to microscopic and IBA calculations.     

Mass spectrometric detection of molecular ions formed by irradiation of condensed methanol with a CO2 laser

IR laser-induced ionization is investigated in condensed methanol (77 K) using a TEA CO₂ laser for resonant vibrational excitation and a quadrupole mass spectrometer to analyse the ion spectra produced by laser irradiation. Ions are already detected at laser fluences below 1 J/cm², far below dielectric breakdown. The fluence dependence of the ion yield is measured for two groups of ions and the total number of ions. A mechanism is proposed for the photochemical production of protonated molecules. The protonated monomer is the species with the highest abundance; however, protonated dimers and other quasimolecular ions and fragment ions are also found.     

High pressure experiments on AlxGa1−xAs-GaAs quantum-well heterostructure lasers

Hydrostatic pressure experiments on Al_xGa_1?xAsGaAs quantum-well heterostructure (QWH) laser diodes are described. Data are presented giving ～11.5meV/kbar for the bandgap vs. pressure coefficient at lower pressures, with a change to 8.5–9meV/kbar at higher pressures. We suggest that this behavior is caused by biaxial and shear stresses in the active region induced by doping or composition mismatch relative to the confining layers, or between the n and p confining layers themselves. A model consistent with the experimental data is presented.     

A model for estimating (p, π+) cross sections

We have formulated a model for estimating the value of the (p, π⁺) cross section on a target nucleus by relating it to the elastic π⁺ scattering cross section on the same target.     

Strangelet search and particle production studies in Pb+Pb collisions at 158 AGeV/c at CERN SPS

We searched for long-lived strange quark matter particles, so-calledstrangelets, and studied particle and antiparticle production in Pb+Pb collisions at 158 GeV/c per nucleon at zero degree production angle. We give upper limits for the production of strangelets covering a mass to charge ratio up to 120 GeV/c ² and lifetimest _lab>1.2 μs and plot invariant differential production cross sections as a function of rapidity for a variety of particles.     

Measurement of ΔσL in pp scattering between 200 and 583 MeV

The main structure around m = 2.15 GeV first observed by the Argonne group in the spin-dependent total cross section Δσ_L is confirmed in the energy range available at SIN. A simultaneous study of the scattered particles at small angles has been carried out with success and gave the spin-correlation parameter A_00kk for the pp elastic scattering and for the reaction pp → π⁺d. The contribution of the 3-body reactions to this spin-dependent total cross section has been deduced and found to be lower than the contribution of the π⁺d reaction even at 583 MeV.     

Diels-alder reactivity of polycyclic aromatic hydrocarbons-5: Theoretical correlations

Second-order rate constants for the Diels-Alder reaction of 90 aromatic hydrocarbons with maleic anhydride, measured spectrophotometrically at 91.5° in 1,2,4-trichlorobenzene, are correlated with various reactivity indices, namely Herndon's structure count ratios, second-order perturbation energies, Brown's paralocalization energies, Hess-Schaad resonance energy differences and Polansky indices. Apart from the latter theory, all methods yield satisfactory correlations, with the Hess-Schaad theory being marginally better. An explanation is given why the Hess-Schaad theory is superior to para-localization theory although both are based on Hückel π-electron energies. The observed regioselectivity is correctly accounted for by all except Polansky's theory which yields incorrect results for certain phenes and starphenes.     

On the Relevance of Plasma Parameters in Nonideal Plasmas

The use of different plasma models for composition calculations of nonideal plasmas can result in very different electron concentrations for the same experimental situation characterized e.g. by the measured temperature and pressure. This gives rise to misunderstandings at comparison of theoretical and experimental results. For extreme conditions i.e. in the region of the supposed plasma phase transition results of solid state physics give us the possibility to rule out some plasma models.     

Fungal upgrading of wheat straw for straw-thermoplastics production

Combining biologic pretreatment with storage is an innovative approach for improving feedstock characteristics and cost, but the magnitude of responses of such systems to upsets is unknown. Unsterile wheat straw stems were upgraded for 12 wk with Pleurotus ostreatus at constant temperature to estimate the variation in final compositions with variations in initial moisture and inoculum. Degradation rates and conversions increased with both moisture and inoculum. A regression analysis indicated that system performance was quite stable with respect to inoculum and moisture content after 6 wk of treatment. Scale-up by 150× indicated that system stability and final straw composition are sensitive to inoculum source, history, and inoculation method. Comparative testing of straw-thermoplastic composites produced from upgraded stems is under way.