High-spin structures of 88Kr and 89Rb: Evolution from collective to single-particle behaviors

The high-spin states of the two neutron-rich nuclei, 88Kr and 89R have been studied from the 18O + 208Pb fusion-fission reaction. Their level schemes were built from triple gamma-ray coincidence data and gamma-gamma angular correlations were analyzed in order to assign spin and parity values to most of the observed states. The two levels schemes evolve from collective structures to single-particle excitations as a function of the excitation energy. Comparison with results of shell-model calculations gives the specific proton and neutron configurations which are involved to generate the angular momentum along the yrast lines.Comment: 12 pages, 9 figures, Physical Review C (2013) in pres

High-spin structures of 136Cs

Odd-odd 136Cs nuclei have been produced in the 18O + 208Pb and 12C + 238U fusion-fission reactions and their gamma rays studied with the Euroball array. The high-spin level scheme has been built up to ~ 4.7 MeV excitation energy and spin I ~ 16 hbar from the triple gamma-ray coincidence data. The configurations of the three structures observed above ~ 2 MeV excitation energy are first discussed by analogy with the proton excitations identified in the semi-magic 137Cs nucleus, which involve the three high-j orbits lying above the Z=50 gap, pi g_{7/2}, pi d_{5/2} and pi h_{11/2}. This is confirmed by the results of shell-model calculations performed in this work.Comment: 6 pages, 4 figures, 3 table

Large Deformation Effects in the N = Z 44Ti Compound Nucleus

The N = Z 44Ti* nucleus has been populated in Fusion Evaporation process at very high excitation energies and angular momenta using two entrance channels with different mass-asymmetry. The deformation effects in the rapidly rotating nuclei have been investigated through the energy distribution of the alpha-particle combined to statistical-model calculations. In the case of low-multiplicity events, the ratio between first particle emitted has been measured and shows significant disagreement with the predictions of the statistical-model. This may explain The large discrepancies observed in proton energy spectra measured in previous experiments performed in the same mass region.Comment: Proceeding of the 10th International Conference on Nuclear Reaction Mechanisms, Varenna Italy, June 9-13 2003. 10 pages, 6 figures, 1 tabl

High-spin states with seniority v=4,4,6 in 119-126Sn

The 119-126Sn nuclei have been produced as fission fragments in two reactions induced by heavy ions: 12C+238U at 90 MeV bombarding energy, 18O+208Pb at 85 MeV. Their level schemes have been built from gamma rays detected using the Euroball array. High-spin states located above the long-lived isomeric states of the even- and odd-A 120-126Sn nuclei have been identified. Moreover isomeric states lying around 4.5 MeV have been established in 120,122,124,126Sn from the delayed coincidences between the fission fragment detector SAPhIR and the Euroball array. The states located above 3-MeV excitation energy are ascribed to several broken pairs of neutrons occupying the nu h11/2 orbit. The maximum value of angular momentum available in such a high-j shell, i.e. for mid-occupation and the breaking of the three neutron pairs, has been identified. This process is observed for the first time in spherical nuclei.Comment: 20 pages, 22 figures, 12 tables, accepted for publication in Physical Review

Observation of the lowest energy gamma-ray in any superdeformed nucleus : 196Bi

New results on the superdeformed $^{196}$Bi nucleus a re reported. We have observed with the EUROBALL IV $\gamma$-ray spectrometer array a superdeformed trans ition of 124 keV which is the lowest observed energy $\gamma$-ray in any superdeformed nucleus. We have de velopped microscopic cranked Hartree-Fock-Bogoliubov calculations using the SLy4 effective force and a realistic surface p airing which strongly support the $K^\pi=2^-$($\pi$[651]1/2$\otimes \nu$[752]5/2) assignment of this su perdeformed band

Search for Fingerprints of Tetrahedral Symmetry in 156Gd^{156}Gd

Theoretical predictions suggest the presence of tetrahedral symmetry as an explanation for the vanishing intra-band E2-transitions at the bottom of the odd-spin negative parity band in $^{156}Gd$. The present study reports on experiment performed to address this phenomenon. It allowed to determine the intra-band E2 transitions and branching ratios B(E2)/B(E1) of two of the negative-parity bands in $^{156}Gd$.Comment: presented by Q.T. Doan at XLII Zakopane School of Physics: Breaking Frontiers: Submicron Structures in Physics and Biology, May 2008. 5 pages, minor corrections. To be published in the proceeding

Medium-spin states in neutron-rich 83As and 81As

The 83,81 As nuclei have been produced as fission fragments in the fusion reaction 18O + 208Pb at 85 MeV bombarding energy and studied with the Euroball array. Medium-spin states of 83,81 As have been established up to ∼3.5 MeV excitation energy. From angular correlation analysis, spin values have been assigned to most of the 81 As excited states. The behaviors of the yrast structures identified in this work are discussed in comparison with the general features known in the mass region. Then they are compared to the results of two theoretical approaches: the "rotor + quasiparticle" for 81 As and the shell model using the effective interactions JUN45 for 83,81 As

Proceedings of the third French-Ukrainian workshop on the instrumentation developments for HEP

The reports collected in these proceedings have been presented in the third French-Ukrainian workshop on the instrumentation developments for high-energy physics held at LAL, Orsay on October 15-16. The workshop was conducted in the scope of the IDEATE International Associated Laboratory (LIA). Joint developments between French and Ukrainian laboratories and universities as well as new proposals have been discussed. The main topics of the papers presented in the Proceedings are developments for accelerator and beam monitoring, detector developments, joint developments for large-scale high-energy and astroparticle physics projects, medical applications.Comment: 3rd French-Ukrainian workshop on the instrumentation developments for High Energy Physics, October 15-16, 2015, LAL, Orsay, France, 94 page

New high-spin states of 58142^{142}_ {58}Ce and 56140^{140}_{56}Ba from fusion-fission reactions: Proton excitations in the N = 84 isotones

High-spin states in the $^{142}$Ce and $^{140}$Ba nuclei have been populated in the $^{12}$C + $^{238}$U and $^{18}$O + $^{208}$Pb fusion-fission reactions at 90 MeV and 85 MeV bombarding energy, respectively. The emitted $\gamma$-radiation was detected using the Euroball III and IV arrays. The high-spin yrast and near-to-yrast structures of $^{142}$Ce have been considerably extended. The level scheme of $^{140}$Ba has been extended by six new levels. The newly observed structures in these N = 84 isotones are discussed by analogy with the neighbouring nuclei