Laser Spectroscopy Studies in the Neutron-Rich Sn Region

We propose to use the powerful laser spectroscopy method to determine the magnetic moment $\mu$ and the variation of the mean square charge radius ($\delta\,\langle$r$_{c}^{2}\,\rangle$) for ground and long-lived isomeric states of the Sn isotopes from A=125 to the doubly-magic $^{132}$Sn isotope and beyond. For these neutron-rich Sn nuclei, numerous $\delta\,\langle$r$^{2}_{c}\,\rangle$ curves have already been calculated and the predictions depend upon the effective interactions used. Therefore, a study of the effect of the shell closure N=82 on the $\delta\,\langle$r$^{2}_{c}\,\rangle$ values in the Z=50 magic nuclei is of great interest, especially because $^{132}$Sn is located far from the stability valley. It will help to improve the parameters of the effective interactions and make them more suitable to predict the properties of exotic nuclei. \\ \\The neutron-rich Sn isotopes produced with an uranium carbide target, are ionized using either a hot plasma ion source or the resonant ionization laser ion source RILIS. In both cases the purity of the ion beam is not perfect. Then, getting accurate results beyond A=132 is a challenge. Therefore, we will use the most suitable method depending on the experimental conditions : collinear laser spectroscopy on fast beam or resonant ionisation spectroscopy on laser desorbed beam using the COLLAPS and COMPLIS setup respectively. For Sn heavier than $^{134}$Sn, performing measurements directly on the ion beam delivered by RILIS is planned as a later step, now under investigation. This method will enable us to extend measurements, that are impossible otherwise, to other elements for both neutron-rich and neutron-deficient isotopes very far from stability.