ION STORAGE AND LASER-INDUCED FLUORESCENCE MEASUREMENTS IN AN RFQ TRAP

A radio-frequency quadrupole (RFQ) ion trap has been constructed for l aser spectroscopic measurements of isotope shifts (IS) and hyperfine s tructures (HFS) with a small number of ions produced from a very dilut e hafnium sample placed inside the RFQ trap. The target. atoms are eva porated by a Nd:YAG heating laser pulse, and then selectively ionized by resonance ionization. Through repetitive application of this proced ure, hafnium ions are accumulated in the trap, and a storage time of h ours has been achieved with H-2 as a buffet gas. Laser-induced fluores cence (LIF) with the 5d6s(2) (a D-2) (J = 3/2) - 5d 6s (a D-3)6p (z F- 4(0)) (J = 5/2) transition is observed. Through an RF phase timing coi ncident technique, a resolution of about 1 GHz can be obtained, suffic ient to resolve most of the hyperfine components of the odd A isotopes . Also, by continuously monitoring the LIF signal, the ion cooling tim e in the RFQ trap is measured as a function of buffer gas pressure, an d the ion-molecule collision cross section deduced is consistent with theoretical expectations. The sensitivity of this method was tested wi th the IS measurement of a mass separated Hf-172 source.