Patent ID: 6924478

Claim:
Method of tandem mass spectrometry comprising the steps of a) accumulating positive or negative sample ions for a period of time in an ion trap; b) providing a cloud of electrons inside the trap with sufficiently low kinetic energy, below approximately 100 eV, to allow ion-electron reactions by which a fraction of the ions, but not all ions, dissociate into fragment ions; c) detecting the mass-to-charge ratios of the fragment ions, whereby the undissociated ions remain inside the trap during and after the detection; d) exciting the undissociated ions vibrationally, whereby at least some of the ions dissociate into fragment ions; and e) detecting the mass-to-charge ratios of the fragment ions, thus allowing recordings of fragment mass spectra from both ion-electron reactions and vibrational excitation from the same accumulation of sample ions.