Interaction of 17F with a 208Pb target below the Coulomb barrier

The interaction of loosely bound (S _p = 600 keV) ¹⁷F ions with a ²⁰⁸Pb target was studied at E _lab = 86 MeV, below the Coulomb barrier, by measuring the differential cross-section for the quasi-elastic scattering and the cross-section for the exclusive breakup process ¹⁷F $ \rightarrow$ ¹⁶O + p . The small reaction and exclusive breakup cross-sections confirm the small reactivity of this system, even at low energy, and indicates that the ¹⁷F small binding energy plays a minor role in the reaction dynamics.     

High-spin states in the 96Tc nucleus

High-spin states in the ⁹⁶Tc nucleus have been studied with the reactions ⁸²Se(¹⁹F,5nγ) at 68 MeV and Zn(³⁶S,αpxn) at 130 MeV. Two γ-ray cascades (irregular bandlike structures) have been observed up to an excitation energy of about 10 MeV and spin 21-22?. Received: 19 January 2001 / Accepted: 30 March 2001     

Strong reaction channels at barrier energies in the system 6Li + 208Pb

Large cross-section reaction channels were measured in the systems ⁶Li( ⁷Li) + ²⁰⁸Pb with high statistical accuracy at 5(3) energies around the Coulomb barrier from 29 to 39 MeV. These channels were assigned (mainly) to the breakup of ⁶Li, very loosely bound, into α + d and to the breakup of ⁵Li, produced by n-transfer to the target, into α + p and to similar processes with ⁷Li beam. The cross-sections with ⁶Li, S _α = 1.475 MeV, are systematically larger than the ⁷Li ones. This reflects, most likely, the higher binding energy of ⁷Li, S _α = 2.468 MeV. Theoretical predictions for the ⁶Li + ²⁰⁸Pb system which include for ⁶Li breakup to continuum states within a continuum discretized coupled-channels approach (CDCC) and resonant breakup plus n-transfer with DWBA reproduce the angular distribution shapes but still underestimate the cross-sections by a factor ∼ 3. Received: 15 January 2001 / Accepted: 3 March 2001     

Recent developments and on-line tests of uranium carbide targets for production of nuclides far from stability

The capacity of uranium carbide target materials of different structure and density for production of neutron-rich and heavy neutron-deficient nuclides have been investigated. The yields of Cs and Fr produced by a 1 GeV proton beam of the PNPI synchrocyclotron and release properties of different targets have been measured. Yields and release efficiencies of Cs and Fr produced from a high density UC target material and from low density UCx prepared by the ISOLDE method at IRIS in the collaboration with PARRNe group from Orsay are compared. The yields from ISOLDE original target are presented for comparison as well.     

Elastic scattering for the system 11Be + 209Bi at Coulomb barrier energies

The elastic scattering process for ¹¹Be ions impinging on a ²⁰⁹Bi target was studied in the energy range around the Coulomb barrier. The angular distributions of the ¹¹Be scattered particles were analyzed within the optical model framework in order to evaluate the reaction cross section, which turned out to be much larger than the fusion one, especially in the sub-barrier region. The comparison with the system ⁹Be + ²⁰⁹Bi showed that the reaction cross section is larger for the reaction ¹¹Be + ²⁰⁹Bi in the energy range around the Coulomb barrier, while they are rather similar at higher bombarding energies. This result suggests that direct processes related to the ¹¹Be halo structure and lower binding energy are more relevant at near-barrier energies.     

Excitation of 6 Li above the breakup threshold in the 6 Li + 208 Pb system around the Coulomb barrier

The excitation energy above the breakup threshold of the Li system, after the interaction of ⁶Li nuclei with a ²⁰⁸Pb target, was deduced from the invariant mass of the system. Data were collected with a large-solid-angle detector set-up at four beam energies around the Coulomb barrier. The excitation of the ⁶Li nucleus above the breakup threshold (1.47 MeV) has a quite similar behavior at each measured beam energy and angle; it is peaked at MeV above the threshold and shows an exponential decay on the high energy side, which is a clear signature of a direct breakup process. The experimental excitation energies are reproduced both in shape and absolute value by 1) fully quantum-mechanical Coupled-Channel calculations with coupling to discretized-continuum ⁶Li excitations, 2) semi-classical Coupled-Channel approach, where the relative motion is treated along a classical trajectory.Received: 2 June 2003, Published online: 18 November 2003PACS: 25.70.Ji Fusion and fusion-fission reactions - 25.70.Mn Projectile and target fragmentation - 24.10.Eq Coupled-channel and distorted-wave modelsThis revised version was published online in December 2003 with corrections to the communicators name.     

High-spin states in the <Superscript>97</Superscript>Tc nucleus

High-spin states in the ⁹⁷Tc nucleus have been studied by in-beam γ-ray spectroscopy with the reaction ⁸²Se(¹⁹F,4nγ) at 68 MeV incident energy. Excited states have been observed up to about 8 MeV excitation and spin 43/2. The observed level scheme is compared with results of shell model calculations. Received: 22 November 2002 / Accepted: 23 December 2002 / Published online: 18 March 2003 RID="a" ID="a"e-mail: bucurescu@tandem.nipne.ro RID="b" ID="b"Present address: INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy. RID="b" ID="b"Present address: INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy. RID="b" ID="b"Present address: INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy. RID="c" ID="c"Present address: Università di Padova, Padova, Italy. Communicated by C. Signorini     

Dissociation and vibrational excitation of cold HD<Superscript>+</Superscript> by electron impact

We have investigated the competition between dissociative excitation, dissociative recombination and vibrational excitation processes taking place in the reactive collisions of vibrationally cold HD⁺ with electrons. The energy range 1–12 eV has been considered.     

Low-spin excitations in 146Sm

The low-spin excitations of the nucleus ¹⁴⁶Sm which is just two neutrons and two protons away from the N = 82 shell and Z = 64 subshell closures have been investigated by means of the ¹⁴³Nd (??, n) and ¹⁴⁴Nd (??, 2n) fusion-evaporation reactions. We established 47 hitherto unknown energy levels up to 4.7MeV and 75 new transitions. In addition, 7 spin assignments were possible from the ??-?? angular correlation analysis. The structure of the possible candidates for a 2⁺ ? 3^? quadrupole-octupole multiplet are first discussed in terms of the harmonic vibrational model. A comparison of these states with the corresponding ones in the neighboring N = 84 isotones is also presented. Finally, the structure of the ¹⁴⁶Sm nucleus is interpreted in terms of the IBA-spdf model. It is shown that the model is able to reproduce the experimental relative transition strengths of the 2⁺ ? 3^? quadrupole-octupole multiplet and also a series of collective properties such as the proposed double-octupole excitations.