Frequency tripling for resonance ionization spectroscopy (RIS) of Cd

To explore the nucleosynthesis of heavy elements in the rapid neutron-capture process, investigations on short-lived, very neutron-rich Cd isotopes are planned that require pure samples. These will be produced at the CERN-ISOLDE on-line mass separator in combination with a chemically selective laser ion source. The excitation scheme for resonance ionization of Cd was tested in Mainz with a copper-vapor-pumped dye laser system. Due to the high ionization potential of Cd, frequency tripling was required for the first excitation step (lambda(1) = 228.8 nm). Laser light with an average power of 2 mW was obtained after frequency tripling and was successfully used for RIS test measurements on cadmium with a time-of-flight mass spectrometer. The eight stable Cd isotopes could be identified unambiguously.