MASS-SPECTRA FORMATION FROM CHARGED MICROPARTICLES

Mass spectra formation during high velocity impact of charged micropar ticles for velocities below 3 km . s(-1) is described. The time-of-fli ght mass spectrometer with the mass resolution R(10%) = 170 for M = 12 0 amu was used. The instrument permits mass spectra registration for m icroparticles with masses ranging from 10(-10) g to 10(-15) g and velo cities above 1 km . s(-1). High velocity microparticles were generated by an electrostatic accelerator. The physical processes of ion genera tion during high velocity impact of charged microparticle have been co nsidered. The field electron emission (hereinafter referred to as auto emission) processes have a dominant role in ion generation at the stag e of the particle approaching the target. There are three mechanisms f or 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 surf ace and the thermal ionization of the surface is the second mechanism. The third one is the thermal ionization of the heated vapor. The resu lts of experimental investigations satisfactorily correlate with the p rocesses described.