Karl Oskar Zell

Electromagnetic properties of some odd-odd nuclei in the A≈ 100 region and IBFFM description of 106Ag

Abstract Electromagnetic properties of odd-odd transitional nuclei with A ≈ 100 are investigated experimentally and theoretically. Nanosecond isomers are studied in-beam by means of delayed γγ-coincidences and the generalized centroid-shift method. The reactions 98 Mo+30MeV 7 Li and 92,94 Mo+ 50 MeV 12 C are utilized. Following half-lives are determined: T 1 2 (547.2 keV in 102 Rh) = 0.25±0.07ns, T 1 2 (243.1 keV in 102 Rh) = 0.30±0.10ns, T 1 2 (181.1 keV in 99 Tc) = 3.8 ± 0.3ns, T 1 2 (2902.0keV in 104 Cd) = 0.6±0.1 ns, T 1 2 (118.7keV in 103 Pd) =0.8±0.2 ns, T 1 2 (131.1 keV in 105 Cd) = 1.5 ±0.3 ns, T 1 2 (211.8 keV in 104 Ag) = 1.4±0.1 ns, T 1 2 (181.0 keV in 102 Ag) = 3.5±0.2 ns. Additionally, several upper limits of level lifetimes are derived. The systematics of E1, M1 and E2 transition rates in 100,102,104 Rh and 102,104,106 Ag is presented and discussed. Fast M1 transitions within the 2qp π g 9 2 ν h 1 2 band appear to be associated with the strong coupling of the π g 9 2 proton and the rotational alignment of the h 11 2 neutron. Extensive IBFFM calculations of level energies and electromagnetic properties of 106 Ag as a typical case demonstrate that this model could account for the complex structural pattern of this type of nuclei. NUCLEAR REACTIONS 98 Mo( 7 Li, 3n), ( 7 Li2nα), E =30 MeV; 92,94 Mo( 12 C, pn), 94 Mo( 12 C, 2n), ( 12 C, 2pn), E = 50 MeV; measured E γ , I γ , γγ ( t ). 102 Rh, 99 Tc, 102,104 Ag, 104 Cd,

Enhanced collectivity along the N = Z line: lifetime measurements in 44Ti, 48Cr, and 52Fe

Lifetimes of the states in 44Ti, 48,50Cr, and 52Fe were determined with high accuracy exploiting the recoil distance Doppler-shift method. The reduced E2 transition strengths of 44Ti and 52 Fe differ considerably from previously known values. A systematic increase in collectivity is found for the N = Z nuclei compared to neighboring isotopes. The B(E2) values along the Ti, Cr, and Fe isotopic chains are compared to shell-model calculations employing established interactions for the 0f 1p shell, as well as a novel effective shell-model Hamiltonian starting from a realistic nucleon-nucleon potential. The theoretical approaches underestimate the B(E2) values for the lower-mass Ti isotopes. Strong indication is found for particle-hole cross-shell configurations, recently corroborated by similar results for the neighboring isotone 42 Ca. A detailed manuscript has meanwhile been published in Physics Letters B [1].

Development of a new Recoil Distance Technique using Coulomb Excitation in Inverse Kinematics

We report on an experiment using Coulomb excitation in inverse kinematics in combination with the plunger technique for measuring lifetimes of excited states of the projectiles. Aside from the investigation of E(5) features in 128Xe, the aim was to explore the special features of such experiments which are also suited to be used with radioactive beams. The measurement was performed at the JYFL with the Koln coincidence plunger device and the JUROGAM spectrometer using a 128Xe beam impinging on a natFe target at a beam energy of 525 MeV. Recoils were detected by means of 32 solar cells placed at extreme forward angles. Particle‐gated γ‐singles and γγ‐coincidences were measured at different target‐degrader distances. Details of the experiment and first results are presented.