Abstract

A number of researchers have shown that sensitive optical measurements can be performed on single microparticles levitated in particle traps. In fact, we have shown that single fluorescent molecules can be detected in microdroplets held in an electrodynamic trap. Further chemical characterization of a microparticle can be achieved by mass spectroscopically analyzing the species on the surface or in the bulk of a particle. Our approach to single particle chemical characterization is to first probe a particle levitated in an electrodynamic trap by using optical spectroscopy. Following the nondestructive investigation, an intense laser pulse is used to desorb ions from the particle while simultaneously converting the particle trap to an ion trap. The laser generated ions are confined in the ion trap and subsequently mass analyzed. A number of different species have been desorbed from particles and mass analyzed by using this approach, including metals, quaternary salts, and explosives. Results and discussion will concentrate on the laser desorption/mass spectrometry aspects of these experiments.

© 1992 Optical Society of America