Time-of-Flight Mass Spectrometer Adapted for Studying Charge Transfer, Ion Dissociation, and Photoionization

A time-of-flight mass spectrometer has been modified so that (1) the drift tube can be used as a reaction/collision chamber for kinetic studies of charge transfer, ion dissociation, and similar processes; and (2) ions can be produced in the source by either pulsed or continuous electron or photon beams. Variable potential barriers, produced in the drift tube by means of movable screened retarder grid assemblies, permit parent ions and fragment ions to be separated, identified, and measured after reaction times that are selectively variable within the range 7.197×10−3(m/q)12≤tr≤7.053(m/q)12 μsec,where m/q is the mass-to-charge ratio of the parent ions in amu per electron charge. The kinetic energy range is from 100 to 10 000 eV for positive ions and 3000 eV for negative ions. The residence time of ions within the ionizing region can be varied continuously from 0 to 100 μsec.