Conditional-firing aerosol-fluorescence spectrum analyzer for individual airborne particles with pulsed 266-nm laser excitation.

We report the operation of an aerosol-fluorescence spectrum analyzer capable of selectively measuring the fluorescence spectra of single micrometer-sized aerosol particles as they flow through the instrument. As the particle first traverses a cw 488-nm probe laser beam, the total fluorescence and elastic scattering are measured with photomultipliers. When the photomultiplier output levels meet preset logic conditions, a UV laser (at 266 nm) is fired and the particle fluorescence spectrum is recorded. Fluorescence spectra of biological airborne particles are presented. The ability of the analyzer to capture the fluorescence spectrum of one type of particle while ignoring others, based on the particle characteristics, is also demonstrated.