The
ionization device of the present invention is intended for use in conjunction with an
aerosol TOF MS operating in a
continuous mode and is capable of ionizing particulated substances in a wide range of particle masses. In the illustrated embodiment, the
ionization unit consists of three coaxial cylindrical bodies having a three aligned longitudinal slits for directing
electron beams from externally located
electron gun onto the axially arranged flow of droplets. The cylindrical bodies are connected to
voltage sources so that the external cylindrical body functions as an
anode that extracts electrons from the current-heated filament. The central cylindrical body, in combination with the aforementioned
anode, serves as an
electron-
energy control member for precisely controlling and selecting the energy of electrons that reach the flow of particles, while the inner cylindrical body functions as a decelerating member that can be used for adjusting energy of electrons which reached the flow of particles. The heated filament of each
electron gun, which is used as a source of electrons, is inclined with respect to the aforementioned longitudinal axis whereby modulation applied to the elongated outer
electrode of the
electron gun provides different
ionization conditions for specific particles of predetermined masses for analysis of which the
aerosol TOF MS is tuned.