Supramicrometer particle shadowgraph imaging in the ionization region of a single particle aerosol mass spectrometer

An in situ method to image individual aerosol particles upon desorption/ionization in a single particle aerosol mass spectrometer using shadowgraph imaging is presented and applied directly to determine a 2D spatial distribution of 5.0μm particles. This new technique is complementary to previously reported methods for the determination of focused particle beam profiles and has several advantages, including a very low particle concentration requirement and the ability to collect the image of an individual particle with a correlated mass spectrum. Images are presented for 1.3, 2.1, 3.0, and 5.0μm polystyrene latex spheres. Particle beam profiles are presented in the directions perpendicular and parallel to the particle beam axis. These results are qualitatively compared to those of a complementary particle collection method (dusting) used at Lawrence Livermore National Laboratory to characterize aerosol beam focusing.