Coulomb Excitation of Neutron-Rich Zn Isotopes: First Observation of the 2[sub 1][sup +] State in [sup 80]Zn

Neutron-rich, radioactive Zn isotopes were investigated at the Radioactive Ion Beam facility REX-ISOLDE (CERN) using low-energy Coulomb excitation. The energy of the 2{sub 1}{sup +} state in {sup 78}Zn could be firmly established and for the first time the 2{sup +}{yields}0{sub 1}{sup +} transition in {sup 80}Zn was observed at 1492(1) keV. B(E2,2{sub 1}{sup +}{yields}0{sub 1}{sup +}) values were extracted for {sup 74,76,78,80}Zn and compared to large scale shell model calculations. With only two protons outside the Z=28 proton core, {sup 80}Zn is the lightest N=50 isotone for which spectroscopic information has been obtained to date. Two sets of advanced shell model calculations reproduce the observed B(E2) systematics. The results for N=50 isotones indicate a good N=50 shell closure and a strong Z=28 proton core polarization. The new results serve as benchmarks to establish theoretical models, predicting the nuclear properties of the doubly magic nucleus {sup 78}Ni.