Status of the ACCULINNA-2 project at FLNR

The project of a new and more powerful in-flight fragment separator ACCULINNA-2 at U-400M cyclotron in FLNR, JINR planned to build in addition to the existing separator ACCULINNA is presented. The new separator will provide high intensity RIBs in the lowest energy range (5÷50 MeV/nucleon) which is attainable for in-flight separators. The possibilities for the astrophysics studies at the proposed device are presented. ACCULINNA-2 separator is planned to be constructed in the years 2010-2015. The current status of the project is reported

New insights into the resonance states of H-5 and He-5

The H-5 system was produced in the H-3(t,p)H-5 reaction studied at small CM angles with a 58 MeV tritium ion beam. High statistics data were used to reconstruct the energy and angular correlations between the H-5 decay fragments. A broad structure in the H-5 missing-mass spectrum showing up above 2.5 MeV was identified as a mixture of the 3/2(+) and 5/2(+) states. The data also present an evidence that the 1/2(+) ground state of SH is located at about 2 MeV. Then, the SH and S He systems were explored by means of transfer reactions occurring in the interactions of 132 MeV He-6 beam nuclei with deuterium. In the H-2(He-6,H-3) reaction a T = 3/2 isobaric analog state of H-5 in He-5 was observed at an excitation energy of 22.0 +/- 0.3 MeV with a width of 2.5 +/- 0.3 MeV

g factors of first 2(+) states of neutron-rich Xe, Ba, and Ce isotopes

Using new techniques developed for measuring angular correlations with large detector arrays, the g factors of 2+ states in Xe140,142 are measured for the first time by the method of correlation attenuation in randomly oriented magnetic fields. g factors in Ba146 and Ce146,148 are measured to establish the method by comparison with previous values. The results are discussed in terms of IBM-2 and rotation-vibration models. © 2009 The American Physical Society

Coexistence of octupole deformation and beta and gamma vibrational bands in 148Ce

From γ-γ-γ and γ-γ-γ-γ coincidence studies of spontaneous fission of 252Cf, new high spin states in 148Ce were identified. The octupole bands with s=+1 and s=−1 are expanded with spins with 28+ and 18−, respectively. Importantly, a 1γ vibrational band has been established up to 14+ and a 1β vibrational band up to 6+. The levels in γ and β bands in 148Ce are compared systematically to those in neighboring 150Nd and 152Sm isotones. This comparison informs the role of deformation and shape transition in this mass region. New 3− and 5− members of the s=+1 octupole band were observed

E2/M1 mixing ratios in transitions from the gamma vibrational bands to the ground state rotational bands of 102, 104, 106, 108Mo, 108, 110, 112Ru, and 112, 114, 116Pd

E2/M1 mixing ratios have been measured for transitions from states in the γ vibrational bands (Iγ+) to states in the ground state bands (I+ or [ I- 1 ] +) of the neutron rich, even-even, deformed isotopes, 102, 104, 106, 108Mo, 108, 110, 112Ru, and 112, 114, 116Pd, including from states as high as 9γ+. These measurements were done using the GAMMASPHERE detector array, which, at the time of the experiment, had 101 working HPGe detectors, arranged at 64 different angles. A 62 μCi source of 252Cf was placed inside GAMMASPHERE yielding 5. 7 × 10 11γ-γ-γ and higher coincidence events. The angular correlations between the transitions from the γ-bands to the ground bands, and the pure E2 transitions within the ground band were then measured. These angular correlations yielded the mixing ratios, demonstrating that these transitions are pure or nearly pure E2, in agreement with theory. In order to correct for possible attenuation due to the lifetime of the intermediate state in these correlations, the g-factors of the intermediate states needed to be known. Therefore, the g-factors of the 2+ states in the ground state band have been measured

g-factor and spin-parity assignments of excited states in the N=83 isotones Te-135, I-136, Xe-137, and Cs-138

The g factor of the 15/2- state in Xe137 was measured for the first time by using a newly developed technique for measuring angular correlations with Gammasphere. Spins and parities were assigned to several levels in the N=83 isotones Te135, I136, Xe137, and Cs138. The calculated g factor in the shell-model frame is in good agreement with the measured one in the present work. Shell-model calculations also support our spin-parity assignments. © 2010 The American Physical Society

Technique for measuring angular correlations and g-factors of excited states with large multi-detector arrays: An application to neutron rich nuclei produced by the spontaneous fission of Cf-252

Triple coincidences between prompt γ-rays emitted in the spontaneous fission of 252Cf were measured with Gammasphere. These data are used to measure the angular correlation of cascades of γ-rays from excited states of neutron rich fission fragments stopped in an unmagnetized iron foil. The hyperfine fields in the iron lattice cause attenuations of the angular correlations between γ-rays emitted from the excited states which have sufficiently long lifetimes. This attenuation is measured and used to calculate the g-factors of excited states in many neutron rich nuclei. © 2007 Elsevier B.V. All rights reserved

Search for 4-n cluster in He-8+He-4 collision and 4-n system

status: publishe

New high-spin level schemes and excitation modes of 117,118,119,120,122Cd

High-spin level schemes of 117,118,119,120,122Cd are expanded by analyzing our high-statistics triple- and higher-fold coincidence events of prompt fission γ rays from 252Cf at Gammasphere. Spin/parity assignments were made based on new γ-γ angular correlation measurements and level systematics in the neighboring isotopes. Stretch-aligned band structures observed in low-lying levels in 117,119,121Cd are seen to weaken with increasing spins, with a quasi-rotational degree of freedom manifested at higher spins. The 5 - levels in even-N 118,120Cd were tentatively interpreted as candidates of quadrupole-octupole (QOC) coupling. The model-independent spin versus h{stroke}ω curves for even-N and odd-N Cd isotopes imply quasi-rotational alignment of an h 11/2 neutron pair in the even-N Cd isotopes. The relative energies of the lowest 11/2 -, 9/2 -, 7/2 -, and 15/2 - levels in 117Cd and 119Cd suggest triaxial shapes based on Meyer-Ter-Vehn theory for these odd-N Cd nuclei. For the even-N Cd isotopes evidence of triaxiality may also be provided by the Shell Correction version of the Tilted Axis Cranking model (SCTAC). © 2011 Elsevier B.V

New high-spin level schemes and excitation modes of <SUP>117,118,119,120,122</SUP>Cd

High-spin level schemes of 117,118,119,120,122Cd are expanded by analyzing our high-statistics triple- and higher-fold coincidence events of prompt fission γ rays from 252Cf at Gammasphere. Spin/parity assignments were made based on new γ-γ angular correlation measurements and level systematics in the neighboring isotopes. Stretch-aligned band structures observed in low-lying levels in 117,119,121Cd are seen to weaken with increasing spins, with a quasi-rotational degree of freedom manifested at higher spins. The 5 - levels in even-N 118,120Cd were tentatively interpreted as candidates of quadrupole-octupole (QOC) coupling. The model-independent spin versus h{stroke}ω curves for even-N and odd-N Cd isotopes imply quasi-rotational alignment of an h 11/2 neutron pair in the even-N Cd isotopes. The relative energies of the lowest 11/2 -, 9/2 -, 7/2 -, and 15/2 - levels in 117Cd and 119Cd suggest triaxial shapes based on Meyer-Ter-Vehn theory for these odd-N Cd nuclei. For the even-N Cd isotopes evidence of triaxiality may also be provided by the Shell Correction version of the Tilted Axis Cranking model (SCTAC). © 2011 Elsevier B.V