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The detailed analysis of the ß-delayed fission data of 180T1 is presented. The experiment was performed by producing, a pure beam of 180T1 by means of highly selective resonance laser ionization followed by mass separation with the ISOLDE (CERN, Geneva) isotope separator. A surprising asymmetric mass distribution of fission fragments from 180Hg, the daughter of 180T1 ß decays, was observed. Here, the energy calibration of the silicon detectors, which is crucial for a proper determination of the fission fragments' energy and mass split, is presented and the total kinetic energy and its dependence on the mass split ratio is discussed. A more precise ß-delayed fission probability PßDF(I80T1) = 3.2(2) x 10-3% was deduced. [ABSTRACT FROM AUTHOR]

An exploratory experiment performed at REX-ISOLDE to investigate cluster-transfer reactions with radioactive beams in inverse kinematics is presented. The aim of the experiment was to test the potential of cluster-transfer reactions at the Coulomb barrier as a mechanism to explore the structure of exotic neutron-rich nuclei. The reactions 7Li(98Rb,αxn) and Li7(98Rb,txn) were studied through particle-γ coincidence measurements, and the results are presented in terms of the observed excitation energies and spins. Moreover, the reaction mechanism is qualitatively discussed as a transfer of a clusterlike particle within a distorted-wave Born approximation framework. The results indicate that cluster-transfer reactions can be described well as a direct process and that they can be an efficient method to investigate the structure of neutron-rich nuclei at medium-high excitation energies and spins. [ABSTRACT FROM AUTHOR]

The quasi-SU(3) sequence of the positive parity νg9/2,d5/2,s1/2 orbitals above the N=40 shell gap are assumed to induce strong quadrupole collectivity in the neutron-rich Fe (Z=26) and Cr (Z=24) isotopes below the nickel region. In this paper the position and strength of these single-particle orbitals are characterized in the neighborhood of 68Ni (Z=28,N=40) through the 66Ni(d,p)67Ni one-neutron transfer reaction at 2.95 MeV/nucleon in inverse kinematics, performed at the REX-ISOLDE facility in CERN. A combination of the Miniball γ-array and T-REX particle-detection setup was used and a delayed coincidence technique was employed to investigate the 13.3-μs isomer at 1007 keV in 67Ni. Excited states up to an excitation energy of 5.8 MeV have been populated. Feeding of the νg9/2 (1007 keV) and νd5/2 (2207 keV and 3277 keV) positive-parity neutron states and negative parity (νpf) states have been observed at low excitation energy. The extracted relative spectroscopic factors, based on a distorted-wave Born approximation analysis, show that the νd5/2 single-particle strength is mostly split over these two excited states. The results are also compared to the distribution of the proton single-particle strength in the 90Zr region (Z=40,N=50). [ABSTRACT FROM AUTHOR]

Background: Shell-model calculations crucially depend on the residual interaction used to approximate the nucleon-nucleon interaction. Recent improvements to the empirical universal sd interaction (USD) describing nuclei within the sd shell yielded two new interactions--USDA and USDB--causing changes in the theoretical description of these nuclei. Purpose: Transition matrix elements between excited states provide an excellent probe to examine the underlying shell structure. These observables provide a stringent lest for the newly derived interactions. The nucleus 26Na with 7 valence neutrons and 3 valence protons outside the doubly-magic 16O core is used as a test case. Method: A radioactive beam experiment with 26Na (T1/2 = 1,07s) was performed at the REX-ISOLDE facility (CERN) using Coulomb excitation at safe energies below the Coulomb barrier. Scattered particles were detected with an annular Si detector in coincidence with γ rays observed by the segmented MINIBALL array. Coulomb excitation cross sections of the beam have been obtained by normalization to the well known Coulomb excitation cross sections of the 104Pd target. Results: The observation of three γ-ray transitions in 26Na together with available spectroscopic data allows us to determine E2- and M1-transitional matrix elements. Results are compared to theoretical predictions. Conclusion: The improved theoretical description of 26Na could be validated. Remaining discrepancies between experimental data and theoretical predictions indicate the need for future experiments and possibly further theoretical improvements. [ABSTRACT FROM AUTHOR]

The isotope 176Au has been studied in the complete fusion reaction 40Ca + 141Pr → 176Au + 5n at the velocity filter SHIP (GSI, Darmstadt). The complex fine-structure α decay of two isomeric states in 176Au feeding several previously unknown excited states in the daughter nucleus 172Ir is presented. An α-decay branching ratio of bα = 9.5(11)% was deduced for the high-spin isomer in 172Ir. [ABSTRACT FROM AUTHOR]

Low-energy β-delayed fission of 194,196At and 200,202Fr was studied in detail at the mass separator ISOLDE at CERN. The fission-fragment mass distributions of daughter nuclei 194,196Po and 202Rn indicate a triple-humped structure, marking the transition between asymmetric fission of 178,180Hg and symmetric fission in the light Ra-Rn nuclei. Comparison with the macroscopic-microscopic finite-range liquid-drop model and the self-consistent approach employing the Gogny D1S energy density functional yields discrepancies. This demonstrates once more the need for dynamical fission calculations, because for both models the potential-energy surfaces lack pronounced structures, in contrast to those for the actinide region. [ABSTRACT FROM AUTHOR]

The bound states of 12Be have been studied through a 11Be(d,p)12Be transfer reaction experiment in inverse kinematics. A 2.8 MeV/u beam of 11Be was produced using the REX-ISOLDE facility at CERN. The outgoing protons were detected with the T-REX silicon detector array. The MINIBALL germanium array was used to detect gamma rays from the excited states in 12Be. The gamma-ray detection enabled a clear identification of the four known bound states in 12Be, and each of the states has been studied individually. Differential cross sections over a large angular range have been extracted. Spectroscopic factors for each of the states have been determined from distorted wave Born approximation (DWBA) calculations and have been compared to previous experimental and theoretical results. [ABSTRACT FROM AUTHOR]

A detailed nuclear-decay spectroscopy study of the neutron-deficient isotope 178T1 has been performed using the highly selective Resonance Ionization Laser Ion Source and ISOLDE mass separator (CERN), which allowed a unique isobarically pure beam of 178T1 to be produced. The first identification of the ß-delayed fission of this isotope was made and its probability PßDf(I78T1) = 0.15(6)% was determined. An asymmetric fission fragment mass distribution of the daughter isotope l78Hg (populated by the ß decay of 178T1) was deduced based on the measured fission fragment energies. The fine-structure a-decay pattern of I78T1 allowed the low-energy states in the daughter nucleus 174Au to be studied. [ABSTRACT FROM AUTHOR]

Detailed α-decay studies of 179TIg and its daughter products 175Aug and 17lIrg were carried out in two complementary experiments at the mass separator ISOLDE (CERN) and velocity filter SHIP (GSI). First unambiguous determination of the α-decay properties of 175Aug was performed as follows: Ea = 6433(4) keV, T1/2 = 207(7) ms, and α-decay branching ratio 90(7)%. First determination of the α-decay branching ratios for 179TIg and 171Irg was also made:ba(179TIg) = 60(2)% and ba(171Irg) = 15(2)%. The spins of the ground states in 175Au and 171Ir are established as l/2+. [ABSTRACT FROM AUTHOR]