Development of Slowed Down Beams at the Fragment Separator for FAIR

The feasibility studies of the slowed down beam setup involving deceleration of a 64Ni beam at 250 MeV/u to 13 MeV/u in a thick Al degrader was performed at the FRagment Separator (FRS) at GSI. The experimentally measured energy spread and the nuclear reaction yields in the degrader are in good agreement with simulations

Cluster Interpretation of Properties of Alternating Parity Bands in Heavy Nuclei

The properties of the states of the alternating parity bands in actinides, Ba, Ce and Nd isotopes are analyzed within a cluster model. The model is based on the assumption that cluster type shapes are produced by the collective motion of the nuclear system in the mass asymmetry coordinate. The calculated spin dependences of the parity splitting and of the electric multipole transition moments are in agreement with the experimental data.Comment: 29 pages, 10 figure

Single-particle isomeric states in 121Pd and 117Ru

Neutron-rich nuclei were populated in a relativistic fission of 238U. Gamma-rays with energies of 135 keV and 184 keV were associated with two isomeric states in 121Pd and 117Ru. Half-lives of 0.63(5) microseconds and 2.0(3) micrisecondss were deduced and the isomeric states were interpreted in terms of deformed single-particle states

Invariant-mass and [gamma]-ray spectroscopy using secondary, radioactive ion beams

Coulomb excitation of secondary beams (5 < Z < 20) at energies around 250 .1 MeV was explored at GSI. For low-lying states, 7-ray spectroscopy was utilized, while high-lying excitations were investigated by means of invariant-mass spectroscopy

Multiple β− decaying states in 194 Re: Shape evolution in neutron-rich osmium isotopes

β decays from heavy, neutron-rich nuclei with A∼190 have been investigated following their production via the relativistic projectile fragmentation of an E/A=1 GeV 208Pb primary beam on a ∼2.5 g/cm2 9Be target. The reaction products were separated a

Breakdown of K selection in Hf178

Coulomb activation of the four quasiparticle Kπ=16+ Hf178 isomer (t1/2=31y) has led to the measurement of a set of Eλ matrix elements coupling the isomer band to the ground band. The present data combined with earlier Hf178 Coulomb excitation data have probed the K components in the wave functions and revealed the onset and saturation of K mixing in low-K bands, whereas the mixing is negligible in the high-K bands. The implications can be applied to other quadrupole-deformed nuclei

Spin dependence of K mixing, strong configuration mixing, and electromagnetic properties of Hf178

The combined data of two Coulomb excitation experiments has verified the purely electromagnetic population of the Kπ=4+,6+,8-, and 16+ rotational bands in Hf178 via 2≤ν≤14 K-forbidden transitions, quantifying the breakdown of the K-selection rule with increasing spin in the low-K bands. The γ-, 4+, and 6+ bands were extended, and four new states in a rotational band were tentatively assigned to a previously known Kπ=0+ band. The quasiparticle structure of the 6+ (t12=77 ns) and 8- (t12=4 s) isomer bands were evaluated, showing that the gyromagnetic ratios of the 6+ isomer band are consistent with a pure π72+[404],π52+[402] structure. The 8- isomer band at 1147 keV and the second 8- band at 1479 keV, thought to be predominantly ν72-[514],ν92+[624] and π92-[514],π72+[404], respectively, are mixed to a degree approaching the strong-mixing limit. Based on measured Kπ=16+ E2 Kπ=0+ matrix elements, it was shown that heavy-ion bombardment could depopulate the 16+ isomer at the ~1% level, although no states were found that would mediate photodeexcitation of the isomer via low-energy x-ray absorption

Broken seniority symmetry in the semimagic proton mid-shell nucleus ⁹⁵Rh

Lifetime measurements of low-lying excited states in the semimagic ( N = 50 ) nucleus 95Rh have been performed by means of the fast-timing technique. The experiment was carried out using γ -ray detector arrays consisting of LaBr3(Ce) scintillators and germanium detectors integrated into the DESPEC experimental setup commissioned for the Facility for Antiproton and Ion Research (FAIR) Phase-0, Darmstadt, Germany. The excited states in 95Rh were populated primarily via the β decays of 95Pd nuclei, produced in the projectile fragmentation of a 850 MeV/nucleon 124Xe beam impinging on a 4 g / cm2 9Be target. The deduced electromagnetic E2 transition strengths for the γ -ray cascade within the multiplet structure depopulating from the isomeric Iπ = 21 / 2+ state are found to exhibit strong deviations from predictions of standard shell model calculations which feature approximately conserved seniority symmetry. In particular, the observation of a strongly suppressed E2 strength for the 13 / 2+ → 9 / 2+ ground state transition cannot be explained by calculations employing standard interactions. This remarkable result may require revision of the nucleon-nucleon interactions employed in state-of-the-art theoretical model calculations, and might also point to the need for including three-body forces in the Hamiltonian