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 5.0 μ m 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 5.0 μ m 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.