We report on the g factor measurement of the isomeric 7− state (E*=2219 keV, T1/2=5.9(8) μs) in the neutron-rich 126Sn nucleus. The nucleus was produced by the fission of a relativistic 238U beam and reaction products were selected by the FRS fragment separator at GSI. For the first time, spin-alignment was observed after relativistic fission. It was used to deduce the g factor of the 7− isomeric state, g(7−)=−0.098(9), from the measured perturbed angular distribution of its γ decay using the RISING Cluster detectors. The observed value confirms the suggested ν(h11/2−1d3/2−1) dominant configuration, which has been proposed for the 7− isomers in neutron-rich Sn isotopes. The failure of the g factor additivity rule and the importance of core polarization evolution with increasing distance from the doubly-magic 132Sn is discussed. The first observation of 18(8)% of spin-alignment produced by the relativistic fission of a 238U beam paves the way to study moments of neutron-rich (sub-)microsecond isomers, which are difficult to align by other means.

. The feasibility of measuring g -factors using the TDPAD method applied to high-energy, heavy fragmentation products is explored. The 2623keV ^π=12^+ isomer in 192 Pb with τ = 1.57 μs has been produced using the fragmentation of a 1 A GeV 238 U beam. The results presented demonstrate for the first time that such heavy nuclei produced in a fragmentation reaction with a relativistic beam are sufficiently well spin-aligned. Moreover, the rather large value of the alignment, 28(10)

The feasibility of measuring g -factors using the TDPAD method applied to high-energy, heavy fragmentation products is explored. The 2623keV \(\ensuremath I^{\pi}=12^+\) isomer in 192Pb with \( \tau\) = 1.57 μs has been produced using the fragmentation of a 1A GeV 238U beam. The results presented demonstrate for the first time that such heavy nuclei produced in a fragmentation reaction with a relativistic beam are sufficiently well spin-aligned. Moreover, the rather large value of the alignment, 28(10)% of the maximum possible, is preserved during the separation process allowing the determination of magnetic moments. The measured values of the lifetime, \( \tau\) = 1.54(9) μs, and the g -factor, g = - 0.175(20) , agree with the results of previous investigations using fusion-evaporation reactions.

New sub-$\ensuremath{\mu}$s isomers have been observed in the neutron-rich Sn isotopes. ${}^{125,127,129}\mathrm{Sn}$ nuclei have been produced in a relativistic fission reaction of $^{238}\mathrm{U}$ on a $^{9}\mathrm{Be}$ target at 750 $A\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{MeV}$ and by the fragmentation of $^{136}\mathrm{Xe}$ at 600 $A\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{MeV}$ populating high-spin yrast states. In addition to the already known $\ensuremath{\mu}$s isomers, three new ones with sub-$\ensuremath{\mu}$s half-lives have been observed. These yrast isomers are the high-spin members of the $\ensuremath{\nu}({d}_{3/2}^{\ensuremath{-}1}{h}_{11/2}^{\ensuremath{-}2})$ and $\ensuremath{\nu}{h}_{11/2}^{\ensuremath{-}n}$, seniority $v=3$ multiplets leading to isomeric ($23/{2}^{+}$) and ($27/{2}^{\ensuremath{-}}$) states, respectively. Added to the already known $19/{2}^{+}\ensuremath{\mu}$s isomers in this region the current work completes the systematic information of neutron-hole excitations toward the filling of the last ${h}_{11/2}$ orbital at $N=82$. The results are discussed in the framework of state-of-the-art shell-model calculations using realistic interactions.

New sub-mu s isomers have been observed in the neutron-rich Sn isotopes. Sn-125,Sn-127,Sn-129 nuclei have been produced in a relativistic fission reaction of U-238 on a Be-9 target at 750 A.MeV and by the fragmentation of Xe-136 at 600 A.MeV populating high-spin yrast states. In addition to the already known mu s isomers, three new ones with sub-mu s half-lives have been observed. These yrast isomers are the high-spin members of the nu(d(3/2)(-1)h(11/2)(-2)) and nu h(11/2)(-n), seniority v = 3 multiplets leading to isomeric (23/2(+)) and (27/2(-)) states, respectively. Added to the already known 19/2(+)mu s isomers in this region the current work completes the systematic information of neutron-hole excitations toward the filling of the last h(11/2) orbital at N = 82. The results are discussed in the framework of state-of-the-art shell-model calculations using realistic interactions.

R. L. Lozeva,1,2,3,* G. S. Simpson,4,5 H. Grawe,6 G. Neyens,1 L. A. Atanasova,2 D. L. Balabanski,7,8,9 D. Bazzacco,10 F. Becker,6 P. Bednarczyk,6,11 G. Benzoni,12 N. Blasi,12 A. Blazhev,13 A. Bracco,12,14 C. Brandau,15 L. Cáceres,6,16 F. Camera,12,14 S. K. Chamoli,17 F. C. L. Crespi,12,14 J.-M. Daugas,18 P. Detistov,2 M. De Rydt,1 P. Doornenbal,6,13 C. Fahlander,19 E. Farnea,10 G. Georgiev,3 J. Gerl,6 K. A. Gladnishki,2,8 M. Górska,6 J. Grębosz,6,11 M. Hass,17 R. Hoischen,19 G. Ilie,13,20 M. Ionescu-Bujor,20 A. Iordachescu,20 J. Jolie,13 A. Jungclaus,16 M. Kmiecik,11 I. Kojouharov,6 N. Kurz,6 S. P. Lakshmi,17 G. Lo Bianco,7,8 S. Mallion,1 A. Maj,11 D. Montanari,12,14 O. Perru,18 M. Pfützner,21 S. Pietri,15 J. A. Pinston,4 Zs. Podolyák,15 W. Prokopowicz,6 D. Rudolph,19 G. Rusev,22 T. R. Saitoh,6 A. Saltarelli,7,8 H. Schaffner,6 R. Schwengner,22 S. Tashenov,6 K. Turzó,1 J. J. Valiente-Dobón,23 N. Vermeulen,1 J. Walker,6,15,16 E. Werner-Malento,6 O. Wieland,12 and H.-J. Wollersheim6 1Instituut voor Kernen Stralingsfysica, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium 2Faculty of Physics, University of Sofia “St. Kl. Ohridski,” BG-1164 Sofia, Bulgaria 3CSNSM, Université Paris-Sud, CNRS/IN2P3, F-91400 Orsay-Campus, France 4LPSC, Université Joseph Fourier Grenoble 1, CNRS/IN2P3, Institut National Polytechnique de Grenoble, F-38026 Grenoble Cedex, France 5Institut Laue-Langevin, F-38042 Grenoble Cedex 9, France 6Gesellschaft für Schwerionenforschung, D-64291 Darmstadt, Germany 7Dipartamento di Fisica, Università degli Studi di Camerino, I-62032 Camerino, Italy 8INFN Sezione di Perugia, I-06123 Perugia, Italy 9Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, BG-1784 Sofia, Bulgaria 10Università degli Studi di Padova and INFN, Sezione di Padova, I-35122 Padova, Italy 11Henryk Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Krakow, Poland 12INFN Sezione di Milano, I-20133 Milano, Italy 13Institut für Kernphysik, Universität zu Köln, D-50937 Köln, Germany 14Università degli Studi di Milano, I-20133 Milano, Italy 15University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom 16Departamento de Fı́sica Teórica, Universidad Autónoma de Madrid, E-28049 Madrid, Spain 17Weizman Institute of Science, 76100 Rehovot, Israel 18CEA/DIF/DPTA/SPN, Bruyères le Châtel, F-91297 Arpajon Cedex, France 19Department of Physics, Lund University, S-22100 Lund, Sweden 20National Institute for Physics and Nuclear Engineering, RO-76900 Bucharest, Romania 21Institute of Experimental Physics, Warsaw University, PL-00681 Warsaw, Poland 22Institut für Strahlenphysik, Forschungszentrum Dresden-Rossendorf, D-01314 Dresden, Germany 23INFN Laboratori Nazionali di Legnaro, I-35020 Legnaro, Italy

The first 2+ states in 134Ce and 136Nd and the second 2+ state in 136Nd were populated by Coulomb excitation at relativistic energies, and γ-rays were measured using the RISING setup at GSI. For 134Ce an indication of the excitation to the second 2+ state was observed. This experiment performed for the first time Coulomb excitation to second 2+ states with rare isotope beams at relativistic energies. For 136Nd the B(E2;21+→0+), B(E2;22+→0+), and B(E2;22+→21+) values relative to the previously known B(E2;21+→0+) value for 134Ce are determined as 81(10), 11(3) and 180(92) W.u., respectively. The results are discussed in the framework of geometrical models that indicate pronounced γ-softness in these nuclei.

The ground-state spins and magnetic moments of neutron-rich Mg-27, Mg-29, and Mg-31 were measured for the first time with laser and beta-NMR spectroscopy at ISOLDE/CERN. The hyperfine structure of Mg-27 observed in fluorescence-confirms previous assignments of the spin I = 1/2 and reveals the magnetic moment mu(I) (Mg-27) = -0.4107(15) mu(N). The hyperfine structure and nuclear magnetic resonance of optically polarized Mg-29-observed in the asymmetry of its beta decay after implantation in a cubic crystal-give I = 3/2 and mu(I) (Mg-29) = +0.9780(6) mu(N). For Mg-31 they yield together I = 1/2 and mu(I) (Mg-31) = -0.88355(15) mu(N), where the negative magnetic moment provides evidence for a positive parity. The results for 27Mg and 29Mg agree well with shell-model calculations confined only to the sd model space, whereas the ground state of Mg-31 involves large contributions from neutrons in the pf shell, which places this nucleus inside the "island of inversion.".

The electric quadrupole moment and the magnetic moment of the 11Li halo nucleus have been measured with more than an order of magnitude higher precision than before, |Q| = 33.3(5) mb and mu = +3.6712(3)muN, revealing a 8.8(1.5)% increase of the quadrupole moment relative to that of 9Li. This result is compared to various models that aim at describing the halo properties. In the shell model an increased quadrupole moment points to a significant occupation of the 1d orbits, whereas in a simple halo picture this can be explained by relating the quadrupole moments of the proton distribution to the charge radii. Advanced models so far fail to reproduce simultaneously the trends observed in the radii and quadrupole moments of the lithium isotopes.

The spectroscopic quadrupole moments of the 11− and 12+ isomers in 192,194Pb, described by the 3s1/2−21h9/21i13/2 intruder two-proton and 1i13/22 two-quasineutron configurations, respectively, have been determined by the method of time-differential observation of the γ-ray perturbed angular distribution. The derived values are |Qs|(12+,192Pb) = 0.32(4) eb, |Qs|(11−,192Pb) = 2.9(3) eb and |Qs|(11−,194Pb) = 3.6(4) eb. The 8+ 2304 keV and 9− 2514 keV states in 192Pb have been identified as isomers, with half-lives of 3.9(3) and 3.3(2) ns, respectively. The experimental spectroscopic quadrupole moments for the 11− and 12+ isomers in neutron deficient Pb nuclei have been described in the framework of the pairing plus quadrupole model. The intrinsic quadrupole moments and deformation of the 11− isomers are compared with the predictions of mean-field and interacting boson models.

Within the RISING (Rare ISotope INvestigations @ GSI) Collaboration at GSI, g factor measurements have been performed on isomeric states in neutron-rich isotopes approaching Sn-132 and in the neutron deficient Pb-region (the g-RISING campaign). We present the experimental technique and some typical aspects related to such studies on relativistic beams selected with the FRS fragment separator. First results are presented for the (19/2(+)) 4.5 mu s isomeric state in Sn-127, which has been produced by means of fission of a relativistic U-238 beam on the one hand, and by the fragmentation of a relativistic Xe-136 beam on the other hand. Spin-alignment has been observed in both reactions. It was the first time that spin-alignment has been established in a relativistic fission reaction.

The first experiments performed using fast fragmentation beams and the RISING gamma-ray spectrometer are reviewed and their results are discussed. Plans for future campaigns using ions which are slowed down and stopped in a catcher will also be presented, including details of experiments which measure magnetic moments (g-factor) and beta decays using an active stopper.

The g factors of 31,32,33Al have been measured using the β-nuclear magnetic resonance (β-NMR) technique on spin-polarized beams produced in the fragmentation of a 36S (77.5 MeV/u) beam on a 9Be target. Nearly pure beams of Al (Z=13) isotopes were selected with the high-resolution fragment separator LISE at GANIL. An asymmetry as high as 6% has been observed in the β-NMR curve for 32Al implanted in a Si single crystal. The magnetic moment of the N=20 nucleus 33Al is obtained for the first time: μ(Al33,Iπ=5/2+)=4.088(5)μN, while those of 31,32Al are obtained with improved accuracy: μ(Al31,Iπ=5/2+)=3.830(5)μN and μ(Al32,Iπ=1+)=1.9516(22)μN. Comparison of the results to shell-model calculations in the sd and the sdpf shell-model spaces leads to the conclusion that 33Al must contain some contribution from 2p–2h intruder configurations in its ground-state wave function. This indicates a gradual transition from the normal sd shell Si (Z=14) isotopes to the intruder Mg (Z=12) isotopes.

The polarization of Al-34 fragments, produced by single neutron pickup from a Be-9 target by a S-36 projectile at 77.5 MeV/nucleon, have been observed at GANIL via the detection of resonantly destroyed beta-asymmetry. The reaction-induced polarization is deduced using a tentative spin/parity assignment for the Al-34 ground state. A positive polarization was measured near the peak of the Al-34 yield curve. A kinematical model based on the spectator-participant model for projectile fragmentation reactions has been extended in order to take into account the features of pickup reactions, i.e., the picked-up nucleon having an average momentum equal to the Fermi momentum and aligned along the incident beam direction. The trend-line in the observed spin-orientation is very well reproduced by this model.

The quadrupole moment of the 8{sup +} yrast state in {sup 84}Kr was measured using the level-mixing spectroscopy technique to be Q= 36(4) e fm{sup 2}. The result is compared with predictions of the shell model using common sets of effective charges. The comparison of experimental quadrupole moments with calculated values for 8{sup +} states in Kr, Sr and Zr isotopes with N= 48, 50 and for 9/2{sup +} states in isotopes with N= 47, 49 suggests a modification of the effective charges used in this region.

The nuclides Mo-92, Mo-98, and Mo-100 have been studied in photon-scattering experiments by using bremsstrahlung produced at an electron energy of 6 MeV at the ELBE accelerator of the Forschungszentrum Rossendorf and at electron energies from 3.2 to 3.8 MeV at the Dynamitron accelerator at the University of Stuttgart. Six dipole transitions in Mo-98 and 19 in Mo-100 were observed for the first time in the energy range from 2 to 4 MeV. The experimental results are compared with predictions of the shell model and with predictions of the quasiparticle random-phase approximation (QRPA) in a deformed basis. The latter show significant contributions of isovector-orbital and isovector-spin vibrations. The change of the magnetic dipole strength in the isotopic chain of the even-mass isotopes from Mo-92 to Mo-100 is discussed. The calculations within the QRPA are extrapolated to the particle-separation energies to estimate the possible influence of M1 strength on the stability of the nuclides against photodissociation in cosmic scenarios.

The quadrupole moment of the 8(+) yrast state in Kr-84 was measured using the level-mixing spectroscopy technique to be Q= 36(4) e fm(2). The result is compared with predictions of the shell model using common sets of effective charges. The comparison of experimental quadrupole moments with calculated values for 8(+) states in Kr, Sr and Zr isotopes with N= 48, 50 and for 9/2(+) states in isotopes with N= 47, 49 suggests a modification of the effective charges used in this region.

R. Schwengner, D. L. Balabanski, G.Neyens, N. Benouaret, D. Borremans, N. Coulier, M.De Rydt, G. Georgiev, S.Mallion G.Rainovski G.Rusev, S. Teughels, K. Vyvey 1 Institut für Strahlenphysik, Forschungszentrum Dresden-Rossendorf, 01314 Dresden, Germany 2 Instituut voor Kernen Stralingsfysica, Katholieke Universiteit Leuven, 3001 Leuven, Belgium 3 Faculty of Physics, St. Kliment Ohridski University of Sofia, 1164 Sofia, Bulgaria