On the α−\alpha-decay of deformed actinide nuclei

$\alpha-$decay through a deformed potential barrier produces significant mixing of angular momenta when mapped from the nuclear interior to the outside. Using experimental branching ratios and either semi-classical or coupled-channels transmission matrices, we have found that there is a set of internal amplitudes which are essentially constant for all even--even actinide nuclei. These same amplitudes also give good results for the known anisotropic $\alpha-$particle emission of the favored decays of odd nuclei in the same mass region. PACS numbers: 23.60.+e, 24.10.Eq, 27.90.+bComment: 5 pages, latex (revtex style), 2 embedded postscript figures uuencoded gz-compressed .tar file To appear in Physical Review Letter

Geowissenschaftliche Untersuchungen on- und offshore Nazca-Platte/Zentralanden an der aktiven suedostpazifischen Subduktionszone. SONNE-Fahrt SO-104. Fahrtabschnitte SO-104/1, SO-104/2 und SO-104/3 Fachlicher Abschlussbericht

The main goal of the CINCA project (Crustal Investigations Off- and Onshore Nazca/Central Andes) was to investigate the structure and evolution of the continental margin of North Chile between 19 S and 26 S. It was postulated that subduction erosion is active, here. During SONNE cruise SO-104, in a multidisciplinary effort German, Chilean and Spanish institutions acquired 4,500 km marine multi-channel seismic data, 8,800 km marine non-seismic data (gravity, magnetics, bathymetric swathmapping and sediment echography), 1,760 km off- and onshore seismic wide-angle/refraction data and seismicity data. Additionally, geological seafloor sampling, geochemical fluid sampling and thermal heat-flow probing was carried out. The results support the hypothesis of subduction erosion basically due to the surface geometries and deep-reaching fracturing of the subducting oceanic crust, lack of an accretionary wedge, the pronounced farctured and extensional character of the continental slope as well as its continuing subsidence since at least Miocene demonstrated by geological sampling. According to the eastward migration of the volcanic arc the ancient continental margin in Early Jurassic times at ca. 200 Ma bp was probably located at more than 200 km west of its modern position and the formerly existing continental crust in this region was removed. Two models of the subduction erosion processes were analyzed in the light of the comprehensive new CINCA results: A - major contributions from the top side of the continental slope and the frontal slope unit, and B - almost all contribution from the base of the continental wedge. Due to higher compatability with the acquired geoscientific data model B is favoured although still some uncertainties exist. The terrace-like shape of the continental middle slope and a structural outer high at its eastern border are observed throughout the entire study area. They are obviously produced by different impact of fluid processes effectuating stronger erosion at the base of the middle slope and hence stronger subsidence. (orig.)SIGLEAvailable from TIB Hannover: F98B2136+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman