Systematical behavior of even-Apolonium isotopes

The energy systematics of even-$A$, neutron-deficient polonium isotopes have been previously observed down to $A=194\mathrm{}$. The low-lying states display a gradual approach to the equal spacings of a harmonic vibrator, exceeding this limit for the first time in ${}^{194}$Po. We have successfully modeled these energy systematics using the particle-core model and have applied the quasiparticle random phase approximation to extract microscopic wave functions for the collective $2_1^{+}$ states and predict ${B(E2;2\mathrm{}}_1^{+}\to 0_1^{+})$ values. We are able to explain the Po trends in terms of the overlaps of the wave functions of valence particles, overlaps which are enhanced when particles occupy the high-$j$ proton ${1h}_{9/2}$ and neutron ${1i}_{13/2}$ orbitals. We find little evidence for particle-hole excitations across the $Z=82\mathrm{}$ shell gap.