Changes in the mean square charge radii of neutron-deficient europium isotopes measured by the laser ion source resonance ionization spectroscopy

The laser ion source has been used for the study of the isotope shifts of neutron-deficient Eu isotopes. The extension of the region of applicability of the method by using the - and -radiation detection is reported. We have measured the isotope shifts of the europium optical line 576.520 nm for . To increase the laser ion source efficiency an axial magnetic field (350 gauss) was applied. Nearly a twofold rise of the ionization efficiency for Eu was observed. By using the effect of optical ion bunching an increase of the selectivity was obtained. The isotope shift data for are in agreement with the previously measured isotope shifts for these nuclides. The new data for and refined data for point to a gradual increase of the deformation for these isotopes. Comparisons with microscopic-macroscopic calculations and calculations in the framework of the Hartree-Fock model were performed.Received: 10 November 2003, Revised: 28 April 2004, Published online: 19 October 2004PACS: 29.25.Rm Sources of radioactive nuclei - 42.62.Fi Laser spectroscopy - 21.10.-k Properties of nuclei; nuclear energy levels - 21.10.Ft Charge distribution