Investigation of the mixed-symmetric one-quadrupole phonon 2⁺₁,ms state of the heavy nucleus ²⁰⁴Hg

Low-energy quadrupole-collective excitations of isovector character, the so-called states with proton-neutron mixed-symmetric character (MSS), have been investigated in ²⁰⁴Hg which is the sole stable nucleus in the straight vicinity of ²⁰⁸Pb exhibiting a 2π — 2ν structure. A ¹²C(²⁰⁴Hg,²⁰⁴Hg*)¹²C projectile Coulomb-excitation experiment at 890MeV was performed at Argonne National Laboratory using the ATLAS accelerator. γ-rays originating from the decay of the excited states of ²⁰⁴Hg were detected using the GAMMASPHERE spectrometer. The measured Coulomb-excitation yields provide the B(M1) and the B(E2) strength distributions which unambiguously reveal the 2⁺₃ state at 1948 keV as the one-phonon MSS of ²⁰⁴Hg.