D. L. Balabanski

g-factor measurements of μs isomeric states in neutron-rich nuclei around 68Ni produced in projectile-fragmentation reactions

We report the first g factor measurement on microsecond isomers of neutronrich nuclei produced in projectile-fragmentation reactions at intermediate energies. The nuclides in the vicinity of 68 Ni were produced and spin oriented following the fragmentation of a 76 Ge, 61.4 MeV u −1 beam at GANIL. The LISE spectrometer was used to select the nuclei of interest. The time-dependent perturbed angular distribution (TDPAD) method was applied in combination with th eh eavy-ion–gamma correlation technique to measure the g factors of 69m Cu (J π = 13/2 + , T1/2 = 350 ns) and 67m Ni (J π = 9/2 + , T1/2 = 13.3 µs). Specific details of the experimental technique and the comparison of the results (|g( 69m Cu) |= 0.225(25) and |g( 67m Ni) |= 0.125(6)) with theoretical calculations are discussed. These results provide another indication of the importance of proton excitations across the Z = 28 shell gap.

Extending the region of triaxial superdeformation: Candidate TSD bands in 174Hf

Abstract Three, possibly four, regularly spaced rotational bands with large dynamic moments of inertia have been identified in 174 Hf. Their properties are consistent with known triaxial superdeformed bands of the Lu/Hf region. Calculations predict substantial triaxial deformation ( γ ≈±17°) for 174 Hf structures with deformation ϵ 2 ≈0.45, despite the fact that 174 Hf is eight neutrons away from the previously established N =94 triaxial superdeformed gap. Shell gaps at N =100 and 106 with γ ⩾15° are predicted for ϵ 2 ≈0.45, and are most likely responsible for the calculated TSD minima in 174 Hf.

g-factors of isomers around N≈40, Z≈28 from time-dependent Larmor precession on spin-aligned projectile-like fragments☆

Abstract First and preliminary results of an experiment aimed at measuring g -factors of isomeric states in neutron-rich nuclei in the vicinity of 68 Ni are reported. Isomers near the predicted N =40 sub-shell closure in 69 Cu, 67 Ni and 66 Co have been populated in the fragmentation of axa0 76 Ge, 61.4xa0MeV/u beam onto a 145xa0mg/cm 2 9 Be target at GANIL. Here we report the results for the 357(2)xa0ns, I π =13/2 + isomer in 69 Cu for which a preliminary gyromagnetic ratio of | g |=0.195(9) was derived. The Larmor precession of the spin-oriented isomeric ensemble was measured by recording γ –ion correlations in axa020xa0μs time window. This pioneering experiment has indicated interesting nuclear structure information and shows promising possibilities for future studies of this kind.

Possible Triaxial Superdeformation in 174 Hf

Four regularly spaced rotational bands with large dynamical moments of inertia, which are consistent with known superdeformed bands in the Lu/Hf region, have been identified in 174Hf. The states were populated in the 130Te(48Ca,4n) reaction at a beam energy of 194 MeV. The Gammasphere array detected the emitted gamma radiation. Ultimate cranker calculations predict substantial triaxial deformation (γ ≈ ±17°) for highly deformed 174Hf structures. However, 174Hf is eight neutrons away from the previously established N = 94 triaxial superdeformed shell gap. Shell gaps at N = 100 and 106 with γ ⩾ 15° are observed when e2 ≈ 0.45, which may be responsible for the predicted TSD minima in 174Hf.

g‐Factor Measurements Of Isomeric States In Neutron Rich Nuclei

We report on the first application of the TDPAD method to measure the g factor of neutron‐rich isomeric states, produced and aligned in a projectile fragmentation reaction. The feasibility of similar measurement opens up a new, unexplored region of the nuclear chart for studies of the magnetic moments of microsecond isomers. Nuclei around 68Ni were produced following the fragmentation of 61.6 MeV/u 76Ge on a 145 mg/cm2 Be target. The isotopes of interest were selected using the LISE spectrometer at GANIL, Caen, France, and were implanted in a high purity Cu foil fixed between the poles of an electromagnet. Two Ge Clover detectors, positioned in a plane perpendicular to the holding magnetic field, were used to observe the rotation of the nuclear spin ensemble and to derive the experimental R(t) function. The experimental result for the isomer in 67Ni (Jπ = 9/2+, T1/2 = 13.3 μs, Ex = 1007 keV), |g| = 0.125(6), is presented herein and is also compared to the theoretical expectations.