Systematical behavior of even- A polonium isotopes

The energy systematics of even-A, neutron-deficient polonium isotopes have been previously observed down to $A=194$. The low-lying states display a gradual approach to the equal spacings of a harmonic vibrator, exceeding this limit for the first time in ¹⁹⁴Po. 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 2₁⁺ states and predict B(E2;2₁⁺→0₁⁺) 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 1h9/2 and neutron 1i13/2 orbitals. We find little evidence for particle-hole excitations across the $Z=82$ shell gap.