Beta decay of 50Ni

The very neutron-deficient isotope ⁵⁰Ni was produced in fragmentation reactions between a A MeV ⁵⁸Ni beam and a ⁹Be target. For the first time the decay of this nucleus was investigated, leading to the determination of the half-life as 12⁺³_-2 ms and the branching ratio for -delayed proton emission of ( )%.Received: 16 April 2003, Published online: 22 July 2003PACS: 21.10.Tg Properties of nuclei; nuclear energy levels: Lifetimes - 23.40.-s decay; double decay; electron and muon capture - 29.30.Ep Charged-particle spectroscopyR. Grzywacz: Present address : Physics Division, ORNL, Oak Ridge, TN 37831-6371, USA.I. Mukha: Present address : Instituut voor Kern- en Stralingsfysika, University of Leuven, B-3001 Leuven, Belgium.     

Brueckner calculations in harmonic-oscillator basis I. The method

The problem of solving the reaction matrix equation in harmonic-oscillator basis is studied. A general approximation of the Pauli operator, diagonal with respect to the centre-of-mass quantum numbers, is derived and method for solving the corresponding Bethe-Goldstone equation is proposed and compared with other methods. The accuracy of the approximation is estimated and found to be satisfactory, especially if the method is applied to the⁴He nucleus, in which case the Pauli corrections to the most importantt-matrix elements vanish.     

Chaotic cascades with Kolmogorov 1941 scaling

We define a (chaotic) deterministic variant of random multiplicative cascade models of turbulence. It preserves the hierarchical tree structure, thanks to the addition of infinitesimal noise. The zero-noise limit can be handled by Perron-Frobenius theory, just like the zero-diffusivity limit for the fast dynamo problem. Random multiplicative models do not possess Kolmogorov 1941 (K41) scaling because of a large-deviations effect. Our numerical studies indicate thatdeterministic multiplicative models can be chaotic and still have exact K41 scaling. A mechanism is suggested for avoiding large deviations, which is present in maps with a neutrally unstable fixed point.     

Long-pulse and CW tests of a 110-GHz gyrotron with an internal,quasi-optical converter

A high-power gyrotron, employing an internal converter that produces a Gaussian-like output mode, has been designed and tested. The tube employed a TE_22.6.1-mode interaction cavity that was designed for operation at a frequency of 110 GHz. An internal converter, consisting of an advanced launcher design and four mirrors, produced a Gaussian mode that had a relatively uniform profile at the tube output window to minimize the peak power density. Tests on the tube resulted in output power levels of 680, 530, and 350 kW for pulse durations of 0.5, 2.0, and 10.0 s, respectively. Measurements of the temperature of the output window were made during the long-pulse tests. Output power levels of 1 MW were achieved under short-pulse (1 ms) operation and the tube was operated at CW power levels in excess of 100 kW     

A peptide-catalyzed asymmetric Stetter reaction

Thiazolylalanine, in appropriately functionalized form, has been found to function as an enantioselective catalyst for an intramolecular Stetter reaction. Incorporation of the residue in a number of environments has resulted in a family of catalysts that promote the cyclization of a test substrate with up to 81% enantiomeric excess.