A shell-model description of 0+ intruder states in even-even nuclei

Shape coexistence in the light Po isotopes

“…6 + 1 ) i n 198 Po [27]. The g-factor of the 8 + 1 state in 198 Po is also known [27] and is consistent with a ( 1h 9=2 ) 2 structure. The interpretation of the light Po isotopes must, therefore, rely upon the energy systematics and additional information obtained in decay measurements [25], which will be discussed later.…”

“…To benoted is the only moderate increase in the quadrupole particle-vibration coupling strength, 2 , with decreasing mass. This is not a pronounced e ect and, besides the expected weak coupling case met in 210 Po, the values of the parameters indicate intermediate coupling for the whole mass range studied.…”

“…Furthermore, the third correction term, V + , i s deduced directly from the position of the 2p-2h state in the closed shell nucleus, as compared to the harmonic prediction. In the case of the Pb nuclei, the intruder 2p-2h states have been interpreted as having an oblate deformation and their mass behavior as being mainly determined by the e ects of the quadrupole interaction [2]. The predictions made for the multiphonon states include, therefore, e ects due to deformation and quadrupole correlations.…”

“…In the treatment of the pairing, the Lipkin-Nogami method [57] was used for an approximate numberprojection. For each 2 value, the total energy was minimized with respect to 4 [54,55,58]. We have used two di erent sets of parameters of the Woods-Saxon potential, in order to investigate the dependence of the results on potential parameters.…”

“…It has been predicted within a shell-model interpretation of intruder states [2] that the maximal energy lowering for an e.g. proton mp-mh con guration should take place at the neutron midshell, where the number of the valence particles is largest and the resulting total proton-neutron interaction energy is strongest.…”