Laser spectroscopy of nuclei far off stability in the region of rare-earth and radium

Systematic studies of nuclear spins, moments and charge radii by the method of collinear laser spectroscopy have been performed in recent years at Gatchina (USSR), at the GSI (Darmstadt) and in particular at the ISOLDE facility at CERN, where about 200 nuclides have been investigated. The method and its further prospects are described. The isotopic shifts of elements in the tin region (Cd, In, Sn) cover the middle of the neutron shell 50<=N<=82. They show a very smooth, almost parabolic variation with N. Radium isotopes have been investigated in the range 208<=A<=232. Spins and moments of the heavier Ra-isotopes indicate single particle states belonging to octupole deformed shape according to theory. Irregularities in the odd even staggering of the isotopic shift also indicate some kind of octupole shape instability. The Ra-nuclei below N = 126 are spherical and behave as their lighter isotones down to Pb and Hg. The majority of data has been obtained in the rare-earth region covering the elements Ba, Eu, Gd, Dy, Er, Yb. In Eu an interesting series of dsub(5/2)-proton moments has been investigated, stretching from 141Eu to 155Eu. The magnetic moments reach a maximum at 145Eu which is a proton hole-state to the double-magic nucleus 146Gd, whereas the quadrupole moments reach a minimum at that point. The isotopic shifts of the rare-earth nuclei investigated cover the shell closure at N = 82 as well as the shape transition region between N = 88 and N = 90. It is shown that the sharp shape transition is restricted to a few elements around Z = 64. It disappears at Z = 56 (Ba) as well as at higher Z, namely at Yb (Z = 70). The two latter elements run steadily from spherical into well-deformed shapes. (author)