Electric dipole transitions near the Z = 50 and N = 82 closed shells

Abstract

We point out that E1 transition rates at the Z = 50 (and N = 82) closed shells, describing the decay of the two-phonon quadrupole-octupole |2 + ⊗ 3 −; 1 −〉 states, of the correct magnitude can be obtained. The mechanism of including 1p-1h admixtures, at the tail of the giant dipole resonance (GDR), into the otherwise collective two-phonon states is at the origin of the observed E1 rates. At the same time, we show how a two-body E1 operator can be constructed that directly deexcites the two-phonon 1 − state. We give an estimate of the effective electric charge needed in this two-body E1 operator.