Polarization and relaxation of radon

Investigations of the polarization and relaxation of $^{209}$Rn by spin exchange with laser optically pumped rubidium are reported. On the order of one million atoms per shot were collected in coated and uncoated glass cells. Gamma-ray anisotropies were measured as a signal of the alignment (second order moment of the polarization) resulting from the combination of polarization and quadrupole relaxation at the cell walls. The temperature dependence over the range 130$^\circ$C to 220$^\circ$C shows the anisotropies increasing with increasing temperature as the ratio of the spin exchange polarization rate to the wall relaxation rate increases faster than the rubidium polarization decreases. Polarization relaxation rates for coated and uncoated cells are presented. In addition, improved limits on the multipole mixing ratios of some of the main gamma-ray transitions have been extracted. These results are promising for electric dipole moment measurements of octupole-deformed $^{223}$Rn and other isotopes, provided sufficient quantities of the rare isotopes can be produced.Comment: 4 pages, 4 figure

A study on the transition between seniority-type and collective excitations in 204Po and 206Po

Low-lying yrast states in 204Po and 206Po have been investigated by the γ-γ fast timing technique with LaBr3(Ce) detectors. Excited states of these nuclei were populated in the 197Au(11B,4n) and the 198Pt(12C,4n) fusion-evaporation reactions, respectively, at the FN-Tandem Facility at the University of Cologne. The lifetimes of the 4+1 states in both nuclei were measured, along with an upper limit for the 2+1 state in 204Po. The preliminary results are discussed in the scope of the systematic behavior of the transition strengths between yrast states in polonium isotopes

Benchmarking the PreSPEC@GSI experiment for Coulex-multipolarimetry on the π(p3 / 2) → π(p1 / 2) spin-flip transition in 85Br

Aydın, Sezgin ( Aksaray, Yazar )A first performance test of the Coulomb excitation multipolarimetry (Coulex-multipolarimetry) method is presented. It is based on a 85Brπp3/2→πp1/2 spin-flip experiment performed as part of the PreSPEC-AGATA campaign at the GSI Helmholtzzentrum für Schwerionenforschung (GSI). Via determination of background levels around the expected 85Br excitations as well as measured 197Au excitations, an upper limit for the M1 transition strength of the 1/21-→3/2g.s.- transition in 85Br and a lower beam time limit for upcoming experimental campaigns utilizing Coulex-multipolarimetry have been inferred. The impact of the use of AGATA in its anticipated 1 π configuration on these estimates is deduced via Geant4 simulations. © 2020, Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature

Lifetimes and electromagnetic transition strength in 124Ba

Lifetimes of excited states of 124Ba were measured by the Recoil Distance Doppler Shift (RDDS) technique. The γ-ray coincidence data were analysed by the Differential Decay Curve method (DDCM). The trend of the experimentally deduced normalized B(E2) values reveals a drop at the 8+1 state, which may be caused by structural changes in the backbending region

Lifetimes and electromagnetic transition strength in

Lifetimes of excited states of 124Ba were measured by the Recoil Distance Doppler Shift (RDDS) technique. The γ-ray coincidence data were analysed by the Differential Decay Curve method (DDCM). The trend of the experimentally deduced normalized B(E2) values reveals a drop at the 8+1 state, which may be caused by structural changes in the backbending region

Identification of the one-quadrupole phonon21,ms+state of 204 Hg

One-phonon states of vibrational nuclei with mixed proton–neutron symmetry have been observed throughout the nuclear chart besides the mass A ≈ 200 region. Very recently, it has been proposed that the 2+2 state of ²¹²Po is of isovector nature. This nucleus has two valence protons and two valence neutrons outside the doubly-magic ²⁰⁸Pb nucleus. The stable isotope ²⁰⁴Hg, featuring two valence-proton and valence-neutron holes, with respect to ²⁰⁸Pb, is the particle-hole mirror of ²¹²Po. In order to compare the properties of low-lying isovector excitations in these particle-hole mirror nuclei, we have studied ²⁰⁴Hg by using the projectile Coulomb-excitation technique. The measured absolute B(M1; 2+2 → 2+1 )strength of 0.20 (2)μ2 N indicates that the 2+2 level of ²⁰⁴Hg is at least the main fragment of the 2+1,ms state. For the first time in this mass region, both lowest-lying, one-quadrupole phonon excitations are established together with the complete set of their decay strengths. This allows for a microscopic description of their structures, achieved in the framework of the Quasi-particle Phonon Model