Identification of the one-quadrupole phonon 21,ms+ state of 204 Hg
R. Stegmann (Institut für Kernphysik, Technische Universität Darmstadt, Darmstadt, Germany); C. Stahl (Institut für Kernphysik, Technische Universität Darmstadt, Darmstadt, Germany); G. Rainovski (Faculty of Physics, University of Sofia, St. Kliment Ohridski, Sofia, Bulgaria); N. Pietralla (Institut für Kernphysik, Technische Universität Darmstadt, Darmstadt, Germany); C. Stoyanov (Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia, Bulgaria); et al - Show all 12 authors
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 22+ state of 212 Po is of isovector nature. This nucleus has two valence protons and two valence neutrons outside the doubly-magic 208 Pb nucleus. The stable isotope 204 Hg, featuring two valence-proton and valence-neutron holes, with respect to 208 Pb, is the particle-hole mirror of 212 Po. In order to compare the properties of low-lying isovector excitations in these particle-hole mirror nuclei, we have studied 204 Hg by using the projectile Coulomb-excitation technique. The measured absolute B(M1;22+→21+) strength of 0.20(2)μN2 indicates that the 22+ level of 204 Hg is at least the main fragment of the 21,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.
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