New isomeric state inAg116

Low-lying collective states in120Cd populated byβdecay of120Ag: Breakdown of the anharmonic vibrator model at the three-phonon level

“…The only decay observed from the (0 + ) member is an E2 transition to the one-phonon 513.5-keV (2 + ) state. As such, the assignment of these two levels as three-phonon states is inconsistent with the data (see figures 22 and 23 from Ref [14]). …”

“…At the three-phonon level, the previously assigned 2 + and 0 + states described as three-phonon states do not decay as would be expected from a multi-phonon state. The 1951.4-keV (2 + ) level decays primarily to the two-phonon 0 + state, while decays to the two-phonon 2 + (1213.1 keV) and 4 + states (1219.5 keV) were not observed in the data [14]. The only decay observed from the (0 + ) member is an E2 transition to the one-phonon 513.5-keV (2 + ) state.…”

“…This discrepancy in the decay of the suggested three phonon 0 + and 2 + states with the U(5) description is a consistent feature in all the well-studied even-even neutron-rich Cd nuclei. Figure 1 shows the decays of the 0 + and 2 + members of the reported three-phonon quintuplet for 112 Cd [9], 114 Cd [10], 116 Cd [14], and 118 Cd [15]. None of these nuclei decay as expected in the IBM-2 framework.…”

“…The proton induced fission products were then mass-separated by the OLTF and deposited on a moving tape collector (MTC). The collected samples were subsequently moved to the counting position located at the center of the CARDS array (Clover Array for Radioactive Decay Spectroscopy), which consisted of three segmented-clover Ge detectors, and a Si conversion-electron spectrometer [22].…”

“…(An example of this type of decay is 22 Na (3 + ) → 22 Ne (0 + ) with a log ft of 14.91 2u [19]). The explanation for this discrepancy must be that these levels are not fed directly but instead are fed from higher energy states in 120 Cd or there is a third undiscovered isomer present in 120 Ag, perhaps similar to the structure of 116 Ag [20].…”