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 the multivalued nature of the response curve. The inversion algorithm simulates particles passing through the instrument, subject to constraints imposed by the instrument (and user) according to the information desired. The inversion technique is robust and should be useful in other aerosol applications as well. The software algorithm source files mentioned in this article are available online at http://taylorandfrancis.metapress.com/openurl.asp?genre=article&id=doi:1 0.1080/02786820490439710 To access this file, click on the issue link for 38(5), then select this article. In order to access the full article online, you must either have an institutional subscription or a member subscription accessed through www.aaar.org