a) Describe the differences in setup of linear and reflector TOF instruments.
An instrumental setup where the ions are travelling on a straight line from the point of their creation to the detector is called linear TOF.
In the reflector TOF analyzer – often abbreviated ReTOF – the reflector acts as an ion mirror that focuses ions of different kinetic energies in time. Commonly, reflector instruments are also equipped with a detector behind the reflector allowing linear mode operation simply by switching off the reflector voltage.
b) Compared to the precursor ions, at what times do fragments from metastable dissociations reach the detector of a linear TOF analyzer?
Metastable decompositions during the flight do not reduce the intensity of a molecular ion signal, because the fragments formed conserve the velocity of the fragmenting ion and are therefore detected at the same time-of-flight as their intact precursors.
In linear TOFs, both the ionic and the neutral fragment do cause a response at the detector. This is the only case of detection of neutrals in MS!