LASER IONIZATION MASS-SPECTROSCOPY OF SINGLE AEROSOL-PARTICLES

We describe an instrument that measures the chemical composition of si ngle aerosol particles. To facilitate detection of volatile species, p articles are analyzed less than 0.5 ms after leaving ambient condition s and without touching any surfaces. Particles are introduced into a v acuum through a differentially pumped nozzle, then cross a He-Ne laser beam. The scattered light provides both size information and the trig ger for an excimer laser that desorbs and ionizes molecules from the p article. Mass spectra with excellent signal to noise have been obtaine d from laboratory and ambient particles 0.3 to 16 mu m diameter.