Theoretical Response of Laser Aerosol Spectrometers and Data Inversion by Stochastic Reconstruction

Abstract

Laser optical particle spectrometers have been used to obtain real-time particle counts and infer mass information over a substantial portion of the PM2.5 mass range by means of dynamic aerosol calibrations. The theoretical response of such instruments is quite calculable, as many authors have demonstrated, but the total response still has some problem areas. This article addresses the theoretical response, comparing the calculations to the instrument calibration and other experimental data. Other instrument characteristics, particularly the particle path through the instrument, affect the total response. When the whole instrument is considered, theoretical predictions of response with changes of index of refraction can be made with some confidence. The calculated response of such spectrometers is nonmonotonic with particle size for most indices of refraction, making inversion of the acquired data difficult. A data inversion algorithm has been devised to incorporate all the response effects and overcome t...