Isobar suppression by photodetachment in a gas-filled rf quadrupole ion guide

A technique based on selective nonresonant laser photodetachment of unwanted negative ion species has been developed for efficient suppression of isobaric contaminants in negative ion beams. A radio-frequency quadrupole ion guide is employed to cool the negative ion beam and dramatically increase the interaction time of the ions with the laser, substantially increasing the efficiency of the photodetachment process. In a proof-of-principle experiment, we achieved 95% suppression of Co−59 ions by photodetachment while under identical conditions 10% of Ni−58 ions were neutralized.