Backbending from band crossing

It is shown that, in some cases, the back-bending phenomenon in the energy levels of even-even deformed nuclei can be explained by the interaction between several rotational bands; the evidence is more complete in the case of three band interaction. The `upper' or `third' band has a moment of inertia close to the rigid-body one, starts at an excitation energy of about 1.5 MeV and interacts very weakly with the ground-state band, and probably also with the beta -vibrational band. Experimental evidences in favour of such a model have been found in /sup 154/Gd, /sup 154/Dy, /sup 156/Dy.Anglai

Large size foil - microchannel-plate timing detectors

To measure the velocity of slow heavy nuclei, created as evaporation residues in nuclear reactions, large area thin timing detectors should be used. An overview is given on principial properties and possibilities of foil -micro-channel plate timing detector units and the properties of many time-of-flight (TOF) systems of this type are analysed. Two new large area foil - micro-channel plate TOF systems are presented: The TOF unit at the velocity separator SHIP, GSI Darmstadt (#approx#55 cm"2 active area, #>=#99% detection efficiency, 100% transparency and #<=#700 ps time resolution) and the TOF system of the electrostatic separator VASSILISSA, JINR Dubna (#approx#50 cm"2 active area, 99.99% detection efficiency, 90% transparency and #approx#500 ps time resolution). Both systems are unique in size and conditions of their exploitation. (orig.)34 refs.Available from TIB Hannover: RA 3692(95-08) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

The new element 111

The new element 111 was produced and unambiguously identified in an experiment at SHIP, GSI Darmstadt. Three nuclei of the isotope "2"7"2111 were observed in irradiations of "2"0"9Bi targets with "6"4Ni projectiles of 318 MeV and 320 MeV energy. The cross-sections are (1.7"+"3"."3_-_1_._4) pb and (3.5"+"4"."6_-_2_._3) pb, respectively. The nuclei decay by #alpha# emission into the new and so far the heaviest isotopes of the elements 109 and 107 with mass numbers A=268 and A=264. The #alpha#-decay chains were followed down to the known nuclei "2"6"0105 and "2"5"6Lr. (orig.)Available from TIB Hannover: RO 801(95-05) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

The new element 112 Short note

The new element 112 was produced and identified unambigiously in an experiment at SHIP, GSI Darmstadt. Two decay chains of the isotope "2"7"7112 were observed in irradiations of "2"0"8Pb targets with "7"0Zn projectiles of 344 MeV kinetic energy. The isotope decays by emission of #alpha# particles with a half-life of (240_-_9_0"+"4"3"0) #mu#s. Two different #alpha# energies of (11.649#+-#20) keV and (11.454#+-#20) keV were measured for the two observed decays. The cross-section measured in three weeks of irradiations is (1.0_-_0_._4"+"1"8) pb. (orig.)Available from TIB Hannover: RO 801(96-09) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Production and decay of "2"6"9110

In an experiment carried out to identify element 110, we have observed an #alpha#-decay chain, that can be unambiguously assigned to "2"6"9110. In a series of preexperiments the excitation functions of the fusion reactions "5"0Ti+"2"0"8Pb#->#"2"5"8104* and "5"8Fe+"2"0"8Pb#->#"2"6"6108* were measured with high precision in order to get the optimum projectile energies for the production of these heavy elements. The cross-section maxima of the 1n evaporation channels were observed at excitation energies of 15.6 MeV and 13.4 MeV, respectively. These data result in an optimum excitation energy of 12.3 MeV of the compound nucleus for the production of "2"6"9110 in the reaction "6"2Ni+"2"0"8Pb#->#"2"6"9110+1n. In irradiations at the corresponding beam energy of 311 MeV we have observed a decay chain of 4 subsequent #alpha# decays. This can be assigned to the isotope with the mass number 269 of the element 110 on the basis of delayed #alpha#-#alpha# coincidences. The accurately measured decay data of the daughter isotopes of the elements 108 to 102, obtained in the previous experiments, were used. The isotope "2"6"9110 decays with a half-life of (270_-_1_2_0"+"1"3"0"0) #mu#s by emission of (11.32#+-#0.020) MeV alpha particles. The production cross-section is (3.3_-_0_2_._7"+"6"."2) Pb. (orig.)SIGLEAvailable from TIB Hannover: RO 801(94-82) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

The Isospin Dependence of the Nuclear Phase Transition Near the Critical Point

The experimental results reveal the isospin dependence of the nuclear phase transition in terms of the Landau Free Energy description of critical phenomena. Near the critical point, different ratios of the neutron to proton concentrations lead to different critical points for the phase transition which is analogous to the phase transitions in He-4-He-3 liquid mixtures. The antisymmetrized molecular dynamics (AMD) and GEMINI models calculations were also performed and the results will be discussed as well

Scattering of 6He at energies around the Coulomb barrier

6 pages, 5 figures.-- El pdf del artículo es la versión pre-print.-- et al.We have measured elastic cross sections of the scattering of 6 He at E-Lab 14, 16, 17, 18 and 22 MeV on Pb-208 in the angular ranges of 20 degrees-64 degrees and 135 degrees-170 degrees. A significant amount of He-4 events is found at energies well below the Coulomb barrier, that becomes dominant above it. Optical model calculations have been performed including a dynamic polarization potential. Very large imaginary diffuseness parameter is needed in order to describe the experimental distributions.This work has been partially supported by the Spanish Dirección General de Investigación, Ciencia y Tecnología under project numbers FPA2000-1592-C03-02, FPA2002-04181-C04-02/04, the Belgian program P5/07 on interuniversity attraction poles of the Belgian-state Federal Services for Scientific, Technical and Cultural Affairs, and the European Community-Access to Research Infrastructure action of the Improving Human Potential Programme, contract no HPRI-CT-1999-00110. AMSB acknowledges a research grant from the Spanish MCyT.This work has been partially supported by the Spanish Dirección General de Investigación, Ciencia y Tecnología under projects number FPA2000-1592-C03-02, FPA2002-04181-C04-02/04, the Belgian program P5/07 on interuniversity attraction poles of the Belgian-state Federal Services for Scientific, Technical and Cultural Affairs, and the European Community-Access to Research Infrastructure action of the Improving Human Potential Programme, contract Nº HPRI-CT-1999-00110. A.M.S.B. acknowledges a research grant from the Spanish MCyT.Peer reviewe