Nuclear shape transition in neutron-deficient gold isotopes

4 pages, 1 table, 4 figures.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.This work has been supported by the Bundesministerium für Forschung und Technologie. One of us, J. Wood was supported in part by the U.S. Department of Energy, Contract DE-AS05-80 ER 10599.Peer reviewe

Sudden change in the nuclear charge distribution of very light gold isotopes

4 pages, 3 tables, 2 figures.-- PACS nrs.: 21.10.Ft, 21.10.Ky, 27.70.+q.On-line resonance-ionization mass spectrometry has been applied to determine the isotope shift and hyperfine structure of 185-189Au and 189mAu in the 6s 2S(1/2)→6p 2p 1/2 (λ=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-color, two-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 β≈0.25 in 186Au and 185Au.This work has been funded by the German Federal Minister for Research and Technology (Bundesminister für Forschung und Technologie) under Contract No. MZ-458-1. One of us {J.L.W.) was supported in part by U.S. Department of Energy Contract No. DE-AS05-80ER10599.Peer reviewe