B. Pietras

Re-examining the transition into the N = 20 island of inversion: Structure of 30Mg

Abstract Intermediate energy single-neutron removal from 31Mg has been employed to investigate the transition into the N = 20 island of inversion. Levels up to 5 MeV excitation energy in 30Mg were populated and spin-parity assignments were inferred from the corresponding longitudinal momentum distributions and γ-ray decay scheme. Comparison with eikonal-model calculations also permitted spectroscopic factors to be deduced. Surprisingly, the 0 2 + level in 30Mg was found to have a strength much weaker than expected in the conventional picture of a predominantly 2 p − 2 h intruder configuration having a large overlap with the deformed 31Mg ground state. In addition, negative parity levels were identified for the first time in 30Mg, one of which is located at low excitation energy. The results are discussed in the light of shell-model calculations employing two newly developed approaches with markedly different descriptions of the structure of 30Mg. It is concluded that the cross-shell effects in the region of the island of inversion at Z = 12 are considerably more complex than previously thought and that n p − n h configurations play a major role in the structure of 30Mg.

How sharp is the transition into the N=20 island of inversion for the Mg isotopes ?

The N=20 island of inversion is an excellent playground for testing shell model calculations. The Mg chain is a region of shell evolution still far from being well understood. In this paper we present preliminary results of a single-neutron knockout experiment from 31Mg performed at GANIL to study the structure of 31Mg and of the core 30Mg. The level scheme and longitudinal momentum distributions were mesured and spectroscopic factors were deduced. Negative parity states arise at low energy and the spectroscopic factor for the isomeric in 30Mg was determined to be smaller than foreseen in the standard picture. The preliminary experimental results are compared to state-of the art shell model calculations revealing opposed interpretations.

Fission dynamics at high excitation energies investigated in complete kinematics measurements

Light-charged particles emitted in proton-induced fission reactions on 208 Pb have been measured at different kinetic energies: 370A, 500A, and 650A MeV. The experiment was performed by the SOFIA collaboration at the GSI facilities in Darmstadt (Germany). The inverse kinematics technique was combined with a setup especially designed to measure light-charged particles in coincidence with fission fragments. The data were compared with different model calculations to assess the ground-to-saddle dynamics. The results confirm that transient and dissipative effects are required for an accurate description of the fission observables.

New experimental approaches to investigate the fission dynamics

The first ever achieved full identification of both fission fragments, in atomic and mass number, made it possible to define new observables sensitive to the fission dynamics along the fission path up to the scission point. Moreover, proton-induced fission of 208Pb at high energies offers optimal conditions for the investigation of dissipative, and transient effects, because of the high-excitation energy of the fissioning nuclei, its low angular momentum, and limited shape distortion by the reaction. In this work we show that the charge distribution of the final fission fragments can constrain the ground-to-saddle dynamics while the mass distribution is sensitive to the dynamics until the scission point.

The CALIFA endcap

D. Cortina-Gil ∗1, H. Alvarez-Pol 1, T. Aumann13, V. Avdeichikov 4, M. Bendel†7, J. Benlliure1, D. Bertini5, A. Bezbakh 11, T. Bloch13, M. Böhmer7, M.J.G. Borge2, J.A. Briz2, P. Cabanelas 1, E. Casarejos 8, M. Carmona Gallardo2, J. Cederk̈all4, L. Chulkov12, M. Dierigl7, D. Di Julio4, G. Ferńandez Maŕ ınez13, E. Fiori10, A. Fomichev 11, D. Galaviz9, R. Gernḧauser7, J. Gerl5, P. Golubev4, M. Golovkov11, D. Gonźalez1, A. Gorshkov 11, A.L. Hartig13, A. Heinz3, M. Heil5, B. Heiss7, A. Ignatov13, B. Jakobsson 4, H.T. Johansson 3, P. Klenze7, D. Köeper5, Th. Kröll13, R. Krücken‡7, S. Krupko11, F. Kurz7, T. Le Bleis7, B. Löher10, E. Nacher 2, T. Nilsson3, A. Perea2, C. Pfeffer7, B. Pietras1, R. Reifarth6, P. Remmels 7, H.B. Rhee13, J. Sanchez del Rio 2, D. Savran10, H. Scheit 13, S. Sidorchuk 11, H. Simon5, O. Tengblad2, P. Teubig9, R. Thies3, J.A. Viĺan8, M. von Schmid13, M. Winkel§7, S. Winkler 7, F. Wamers13, P. Yãnez8, and the RB collaboration. 1Universidad de Santiago de Compostela; 2Instituto Estructura de la Materia, CSIC Madrid; 3Chalmers University of Technology, Göteborg; 4Lund University; 5Helmholtzzentrum für Schwerionenforschung, Darmstadt; 6Goethe University Frankfurt am Main;7Technische Universität München; 8Universidad de Vigo;9Centro de Fı́sica Nuclear da Universidade de Lisboa; 10Extreme Matter Institute and Research Division, GSI; 11Joint Institute for Nuclear Research, Dubna; 12Nuclear Reseach Center, Kurchatov Institute Moscow; 13Technische Universität Darmstadt

Progress report of the CALIFA/

D. Cortina-Gil †1, H. Alvarez-Pol1, T. Aumann13, V. Avdeichikov4, M. Bendel7, J. Benlliure1, D. Bertini5, A. Bezbakh11, T. Bloch13, M. Böhmer7, M.J.G. Borge2, J.A. Briz2, P. Cabanelas1, E. Casarejos8, M. Carmona Gallardo2, J. Cederkäll4, L. Chulkov12, M. Dierigl7, D. Di Julio4, I. Durán1, E. Fiori10, A. Fomichev11, D. Galaviz9, M. Gascón1, R. Gernhäuser7, J. Gerl5, P. Golubev4, M. Golovkov11, D. González1, A. Gorshkov11, A. Heinz3, M. Heil5, B. Heiss7, W. Henning7, G. Ickert5, A. Ignatov13, B. Jakobsson4, H.T. Johansson3, M. Kmiecik14, Th. Kröll13, R. Krücken ‡ 7, S. Krupko11, F. Kurz7, T. Le Bleis7, B. Löher10, A. Maj14, E. Nacher2, T. Nilsson3, A. Perea2, C. Pfeffer7, N. Pietralla13, B. Pietras1, R. Reifarth6, J. Sanchez del Rio2, D. Savran10, S. Sidorchuk11, H. Simon5, L. Schnorrenberger13, O. Tengblad2, P. Teubig9, R. Thies3, J.A. Vilán8, M. von Schmid13, M. Winkel7, S. Winkler7, F. Wamers13, P. Yañez8, and M. Zieblinski14 1Universidad de Santiago de Compostela; 2Instituto Estructura de la Materia, CSIC Madrid; 3Chalmers University of Technology, Göteborg; 4Lund University; 5Helmholtzzentrum für Schwerionenforschung, Darmstadt; 6Goethe University Frankfurt am Main; 7Technische Universität München; 8Universidad de Vigo; 9Centro de Física Nuclear da Universidade de Lisboa; 10Extreme Matter Institute and Research Division, GSI; 11Joint Institute for Nuclear Research, Dubna; 12Nuclear Reseach Center, Kurchatov Institute Moscow; 13Technische Universität Darmstadt; 14Institute of Nuclear Physics PAN, Krakow, Poland