Strong polarization of the residual nucleus in a heavy-ion induced transfer reaction

A strong polarization of 20Ne levels has been observed in the 16O(16O, 12C)20Ne* reaction along an axis perpendicular to the reaction plane. This polarization differs from that reported in the (7Li, t) reaction, when the same nuclear levels were populated. D.W.B.A. calculations which fitted both angular distributions and polarization in the (7Li, t) reaction and which can also describe the (16O, 12C) angular distributions fail to reproduce the associated 20Ne* polarization

Low Energy States of 3181Ga50^{81}_{31} Ga_{50} : Elements on the Doubly-Magic Nature of 78^{78}Ni

Excited levels were attributed to $^{81}_{31}$Ga$_{50}$ for the first time which were fed in the $\beta$-decay of its mother nucleus $^{81}$Zn produced in the fission of $^{nat}$U using the ISOL technique. We show that the structure of this nucleus is consistent with that of the less exotic proton-deficient N=50 isotones within the assumption of strong proton Z=28 and neutron N=50 effective shell effects.Comment: 4 pages, REVTeX 4, 5 figures (eps format

Excited states of 19N and 21O

(18O, 19N) and (18O, 21O) nuclear reactions on a 18O target provide measurements of excited state energies at 1.12 and 1.59 MeV for 19N and at 1.35 and 3.00 MeV for 21O. The 19N mass is remeasured as 15.856 ± 0.050 MeV

Collapse of the N=28 shell closure in 42^{42}Si

The energies of the excited states in very neutron-rich $^{42}$Si and $^{41,43}$P have been measured using in-beam $\gamma$-ray spectroscopy from the fragmentation of secondary beams of $^{42,44}$S at 39 A.MeV. The low 2$^+$ energy of $^{42}$Si, 770(19) keV, together with the level schemes of $^{41,43}$P provide evidence for the disappearance of the Z=14 and N=28 spherical shell closures, which is ascribed mainly to the action of proton-neutron tensor forces. New shell model calculations indicate that $^{42}$Si is best described as a well deformed oblate rotor.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev. let

On the discovery of doubly-magic 48^{48}Ni

The paper reports on the first observation of doubly-magic Nickel-48 in an experimental at the SISSI/LISE3 facility of GANIL. Four Nickel-48 isotopes were identified. In addition, roughly 100 Nickel-49, 50 Iron-45, and 290 Chromium-42 isotopes were observed. This opens the possibility to search for two-proton emission from these nuclei.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev. Let

Release properties of UCx_x and molten U targets

The release properties of UC$_x$ and molten U thick targets associated with a Nier- Bernas ion source have been studied. Two experimental methods are used to extract the release time. Results are presented and discussed for Kr, Cd, I and Xe

Study of the N=50 major shell effect close to 78^{78}Ni : First evidence of a weak coupling structure in 83_32^{83}\_{32}Ge_51\_{51} and three-proton configuration states in 81_31^{81}\_{31}Ga_50\_{50}

New levels were attributed to $^{81}\_{31}$Ga$\_{50}$ and $^{83}\_{32}$Ge$\_{51}$ which were fed by the $\beta$-decay of their respective mother nuclei $^{81}\_{30}$Zn$\_{51}$ and $^{83}\_{31}$Ga$\_{52}$ produced by fission at the "PARRNe" ISOL set-up installed at the Tandem accelerator of the Institut de Physique Nucl\'eaire, Orsay. We show that the low energy structure of $^{81}\_{31}$Ga$\_{50}$ and $^{83}\_{32}$Ge$\_{51}$ can easily be explained within the natural hypothesis of a strong energy gap at N=50 and a doubly-magic character for $^{78}$Ni.Comment: 2 pages, pdf file, To be published in the Proceedings of "International Symposium on Structure of Exotic Nuclei and Nuclear Forces (SENUF 06)", March 2006, Tokyo, Japa

UCx_x target design for the SPIRAL 2 project and the ALTO project

ACC NESTERInternational audienceTwo ways of production of radioactive beams using uranium carbide targets are taken into consideration: fission induced by fast neutrons and by bremsstrahlung radiation. For the SPIRAL 2 project, the fission of 238U in uranium carbide target will be induced by a neutron flow created by bombarding a carbon converter with a 40 MeV high intensity deuteron beam. Calculations and design of the target in order to reach 1013 fissions/s with good release time have been done. The second way is the photofission using an electron beam. In 2005 the ALTO project (Accélérateur Linéaire Auprès du Tandem d'Orsay) will give a 50 MeV/10$\mu$A electron beam. This facility will allow more than 1011 fissions/s. In this case, the electron beam hits the target without converter. Calculations realised in order to estimate the production are used to choose the best target shape. For the two cases some R & D on targets to improve release is described

Projectile Coulomb excitation with fast radioactive beams

5 pages, 5 figures, 1 table.-- PACS nrs.: 23.20.Ck; 27.20.+n.We report a search for γ rays emanating from Coulomb excitation of fast (30-46 MeV/u) radioactive projectiles He-8, Be-11, Be-12, Be-14 interacting with a lead target. These are clearly identified by their Doppler shift. The 320 keV 1/2(-) --> 1/2(+)γ transition from Be-11 was observed with a cross-section of 191 ± 26 mb which is noticeably less than expected from the known lifetime and in the perturbation limit of pure Coulomb excitation. In the other nuclei rather stringent upper limits of 0.01 to 0.2 Weisskopf units, are placed on the hypothetical transition to 1(-) states.We would like to thank F. Geoffroy, R. Hue and L. Petizon for their technical assistance during the experiment, N. Alamanos, G. Baur aud C. Bertulani for discussions and R. Lombard for drawing our attention to the Bertlmann-Martin bound. This work was partly supported by la Région Basse Normandie. One of us, G. Schrieder, would like to thank for the support by the German Federal Minister for Research and Technology (BMFT) under contract 06DA641.Peer reviewe