Nuclear shape transition in neutron-deficient gold isotopes

Abstract

On-line resonance ionization mass spectrometry has been applied to determine the isotope shift and hyperfine structure of 185–189Au and tne I=11/2 isomer of 189Au in the 6s 2S(1/2)-->6p2P(1/2) (h = 268 nm) transition. The Au atoms were obtained as daughters of mass-separated Hg isotopes produced at the ISOLDE facility at CERN, ionized by a three-step resonant photoionization process, detected and mass-selected by time of flight. A drastic change of the nuclear charge radius was observed between 187Au and 186Au, which is interpreted as an onset of strong deformation of β2 ≈ 0.25 in 186Au and 185Au.