Collinear laser spectroscopy of neutron-rich cerium isotopes near the N = 88 shape transition

Laser spectroscopy has been used to measure the isotope shifts of Ce-146 and Ce-148 relative to Ce-144, Z = 58. The new data, in combination with existing optical data on the stable isotopes and radioactive Ce-144 isotope, permits a study of charge radii variations for the even-N Ce nuclei from N = 78 to N = 90. This range covers both the N = 82 shell closure and the N = 88 shape transition region. A marked increase in deformation occurs at N = 88 for elements with Z greater than or equal to 60 but not for those with Z less than or equal to 56. The new data for Ce (Z = 58) show an intermediate behaviour, resulting in a smooth increase in deformation with Z in the N = 88, 90 region.