Improved method for determination of the suppression of isobars in a gas-filled rf quadrupole ion guide

An improved measurement of the limit of isobar suppression by photodetachment has been made. A gas-filled rf quadrupole ion guide was used to slow down negative ions for the purpose of acquiring long interaction times with the applied laser light. A Nd:YAG laser beam (1064nm) was used to selectively deplete a beam of Co- ions inside the rf ion guide and the remaining ions was probed using photodetachment by another Nd:YAG laser and a neutral detector. The neutral detection system allowed for a detection limit more than one order of magnitude better than the previous measurements. With this improved detection method, we show that the suppression of Co- ions was at least four orders of magnitude.