High resolution laser spectroscopy of radioactive isotopes using a RFQ cooler-buncher at CERN-ISOLDE

At CERN, the European Organization for Nuclear Research, radioactive nuclear beams are produced at the On-Line Isotope Mass Separator facility, ISOLDE. This facility provides a variety of exotic nuclear species for multidisciplinary experiments including nuclear physics. A gas-filled linear Paul trap was commissioned off-line and on-line and now is fully integrated at the focal plane of the high resolution separator magnets of ISOLDE. Ion beams with reduced transverse emitance and energy spread are now available for all experiments located downstream the separator beam line. This device is also able to accumulate the ion beam and release the collected sample in short bunches. Typical accumulation times are 100 ms and the released bunch width is 5-20 $\mu{s}$. Such bunching capabilities has substantially increased the sensitivity of collinear laser spectroscopy with fluorescence detection by reducing the background from laser scatter by up to four orders of magnitude. The spectroscopic quadrupole moments of $^{44,46}$K isotopes, as well as the ground-state spins of $^{73,76,78,79}$Ga isotopes and the magnetic dipole moments and spectroscopic quadrupole moments of $^{73,75,76,77,78,79}$Ga isotopes were determined for the first time. The sign of the quadrupole moment of $^{67}$Ga was also unambiguously determined for the first time.