| abstract |
A mass spectrometer is provided that restrains the signal intensity of an MS/MS spectrum from decreasing according to the secondary dissociation of a primary fragment ion generated by a photodissociation. An excitation laser light for causing a photodissociation is irradiated to the trapping space A in the ion trap 1 . At the same time, an excitation signal that does not excite a precursor ion but excites fragment ions is applied to the end cap electrodes 12 and 13 . Since the selected precursor ions gather around the center of the trapping space A, they are irradiated by the excitation laser light and efficiently dissociated. The fragment ions generated by this are immediately excited by the excitation electric field's effect, and are vibrated wildly to be out of the excitation light irradiated space B. Therefore, the fragment ions are not easily irradiated by the excitation laser light and the secondary dissociation does not easily occur. |