By providing size resolved compositional information, the Aerosol Mass Spectrometer (AMS) has greatly advanced understanding of aircraft particulate matter (PM) emissions. AMS data have been critical to much of our understanding of aircraft PM emissions, but in the past it has had limited utility in probing the smallest (<100 nm) particles in the exhaust. Also, prior to this work the AMS has been able to detect only volatile PM and other instruments have been required to characterize the non-volatile (soot). During Phase I, we: 1) developed an improved computational fluid dynamic (CFD) model to simulate the performance of the AMS for <100 particles; 2) used the CFD model to invent a new AMS technology with improved performance for <100 nm particles; and 3) evaluated a newly developed instrument which combines a laser vaporization system with a standard AMS to provide size resolved mass and composition data for soot. During Phase II we propose: 1) upgrade our CFD modeling capability to three-dimensions to evaluate Brownian motion and the effects of fabrication imperfections; 2) fabricate and test the promising lens geometry invented during Phase I; 3) demonstrate the laser vaporization AMS and improved lens design(s) in the laboratory and in the field.