Laser Ionization Mass Spectroscopy of Single Aerosol Particles

We describe an instrument that measures the chemical composition of single aerosol particles. To facilitate detection of volatile species, particles are analyzed less than 0.5 ms after leaving ambient conditions and without touching any surfaces. Particles are introduced into a vacuum through a differentially pumped nozzle, then cross a He-Ne laser beam. The scattered light provides both size infonnation and the trigger for an excimer laser that desorbs and ionizes molecules from the particle. Mass spectra with excellent signal to noise have been obtained from laboratory and ambient particles 0.3 to 16 /Lm diameter.