Measurement of nuclear moments and radii by collinear laser spectroscopy

%IS304 %title\\ \\Collinear laser spectroscopy on a fast beam has proven to be a widely applicable and very efficient tool for measurements of changes in mean square nuclear charge radii, nuclear spins, magnetic dipole and electric quadrupole moments. Recent developments of extremely sensitive non-optical detection schemes enabled for some elements the extension of the measurements towards the very short-lived isotopes in the far wings of the ISOLDE production curves. The gain in sensitivity opens up new perspectives, particularly for measurements on lighter nuclei whose ground-state properties can be interpreted by large scale microscopic calculations instead of the more phenomenologic models used for heavier nuclei.\\ \\ For the sequence of argon isotopes $^{32-40}$Ar and $^{46}$Ar isotope shifts and nuclear moments were measured by optical pumping followed by state selective collisional ionization and detection of the $\beta$-decay. Similarly, the low-background $\alpha$-detection was used to extend earlier results on radon to the very neutron deficient $^{200}$Rn and $^{201}$Rn. Present activities are directed towards an investigation of nuclear charge radii of the neon isotopes. So far this is the lightest element for which the small effect of the nuclear charge distribution on the isotope shift is being resolved. The required accuracy is achieved by a direct optical Doppler shift measurement of the ISOLDE beam energy to about 0.5 eV. Isotope shift measurements on muonic atoms of the stable isotopes provide the basis for the evaluation of absolute radii differences. The spatial extension of the charge distribution will be a crucial test of the proton halo nature of $^{17}$Ne which has been postulated from reaction cross-section measurements.\\ \\ NMR spectroscopy with $\beta$-decay asymmetry detection is used as a complementary technique for measuring nuclear moments. High degrees of nuclear polarization up to 50\% are achieved by optical pumping of the fast beam with circularly polarized laser light. The experimental results for sodium comprise the quadrupole moments of the isotopes $^{20}$Na and $^{26-31}$Na extending from the proton drip-line to the N=20 shell closure. \\ \\ Similarly the magnetic moment of the one-neutron halo nucleus $^{11}$Be is being measured. The beryllium beam is provided by a laser ion source recently developed at ISOLDE. The magnetic moment produced by the halo neutron gives insight into the composition of the 1/2$^{+}$ halo wave function.\\ \\\\ \\\\ \\