Mass spectra formation from charged microparticles

Mass spectra formation during high velocity impact of charged microparticles for velocities below 3 km . s(-1) is described. The time-of-flight mass spectrometer with the mass resolution R(10%) = 170 for M = 120 amu was used. The instrument permits mass spectra registration for microparticles with masses ranging from 10(-10) g to 10(-15) g and velocities above 1 km . s(-1). High velocity microparticles were generated by an electrostatic accelerator. The physical processes of ion generation during high velocity impact of charged microparticle have been considered. The field electron emission (hereinafter referred to as autoemission) processes have a dominant role in ion generation at the stage of the particle approaching the target. There are three mechanisms for ion formation. The first one is the electron stimulated desorption of molecular species from a microparticle surface and their ionization by autoemission electrons. The spot heating of the microparticle surface and the thermal ionization of the surface is the second mechanism. The third one is the thermal ionization of the heated vapor. The results of experimental investigations satisfactorily correlate with the processes described.