Mass spectrometer

Abstract

There is provided a tandem mass spectrometry that, in a quadrupole ion trap, allows small mass-number product ions to be detected without lowering the sensitivity and the resolution. In the quadrupole ion trap, ions are produced by an ion source. Next, the ions are accumulated within a 3-dimensional quadrupole electric field formed by a pair of endcap electrodes and a ring electrode. Finally, the accumulated ions are isolated and dissociated, then being detected. In this quadrupole ion trap, there are provided a mechanism for introducing a laser light, and a mechanism for generating a supplemental alternating-current electric field at the time of the ion dissociation. Moreover, the direction of the supplemental alternating-current electric field and the introduction direction of the laser light are made identical to each other.