We present the results from an experiment dedicated to measure the lifetime of the 2 + 2 state, candidate for the one-phonon mixed-symmetry state, of 208 Po. This nucleus was studied in the α-transfer reaction 204 Pb( 12 C, 8 Be) 208 Po and the lifetime of the 2 + 2 state was determined by utilizing the Doppler-shift attenuation method. The experimental data show that the 2 + 2 state decays with a sizable M 1 transition to the 2 + 1 state revealing its isovector nature. Keywords Lifetimes • Electromagnetic transitions • Transfer reactions • 190≤ A ≤219
The lifetimes of the 2 + 1 and 4 + 1 states of 208 Po were measured in the α-transfer reaction 204 Pb( 12 C, 8 Be) 208 Po by γ-ray spectroscopy utilizing the recoil distance Doppler Shift method. The newly extracted transition strengths alongside with ones of the decay of 2 + 2 state were compared to the results of large-scale shell-model calculations using an effective interaction derived from the realistic CD-Bonn nucleon-nucleon potential. The comparison indicates the importance of the quadrupole isovector excitations in the valence shell for a fine tuning of the two-body matrix elements of the shell-model interaction.
Low-lying yrast states of 204 Po and 206 Po were investigated by the γ -γ fast timing technique with LaBr3(Ce) detectors. Excited states of these nuclei were populated in the 197 Au( 11 B,4n) 204 Po and the 198 Pt( 12 C,4n) 206 Po fusion-evaporation reactions, respectively. The beams were delivered by the FN-Tandem accelerator at the University of Cologne. The lifetimes of the 4 + 1 states of both nuclei were measured, along with an upper lifetime limit for the 2 + 1 state of 204 Po. A comparison between the derived B(E2; 4 + 1 → 2 + 1 ) values and results from simplified empirical two-state mixing calculations suggests that for the 4 + 1 states of even-even polonium isotopes the transition from single particle mode at N = 126 to collective mode, when reducing the number of neutrons, occurs above N = 122.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.