The invention relates to time-of-flight
mass spectrometers for the measurement of
daughter ion spectra (also called fragment
ion spectra or MS / MS spectra) and corresponding measurement methods.According to the invention, the ions of an
ion source are initially accelerated only to an
intermediate level of energy, allowing them to decompose at that
energy level by metastable
decomposition or by collisionally induced fragmentation (CID). The ions are then accelerated in a second step to a
high energy level. Light fragment ions
gain a higher velocity than heavier fragment ions or non-decomposed parent ions. The spectrum of fragment ions can be detected separated by
mass in either linear or reflector mode. An ion selector at the
low energy level selects a
single type of parent ion in order to avoid superpositions with fragment ions of other parent ions. A particularly preferred embodiment raises the potential of ions, for there second acceleration, during their flight through a small electrically isolated flight path chamber.