In-gas-cell laser ionization spectroscopy at KISS

We have developed the KEK Isotope Separation System (KISS) at RIKEN to study the nuclear structure of the nuclei in the vicinity of neutron magic number \(N=\) $N=$ 126 from the astrophysical perspective. These neutron-rich nuclei have been produced by using multinucleon transfer (MNT) reactions with combinations of the low-energy \(^{136}\) ${}^{136}$ Xe beam and the production targets of W, Ir, and Pt. At the KISS facility, radioisotopes are ionized by applying in-gas-cell laser ionization technique. In this process, we can perform laser ionization spectroscopy of the refractory elements with the atomic number \(Z=\) $Z=$ 70–78 such as Hf, Ta, W, Re, Os, Ir, and Pt, which cannot be performed in other facilities. Laser spectroscopy can effectively investigate nuclear structure through the measured magnetic moments, isotope shifts (IS) \(\Delta \nu \) $\mathrm{\Delta }\nu$ , changes in the mean-square charge radii \(\delta <r^2>\) $\delta <r^2>$ , and quadrupole deformation parameters \(|<\beta ^2_2>|^{1/2}\) $|<{\beta }_2^2{>|}^{1/2}$ . We have studied the ionization schemes of these elements through offline tests and performed in-gas-cell laser ionization spectroscopy of these refractory neutron-rich nuclei produced at KISS.