Composition measurement of aerosols of submicrometer particles by phase fluctuation absorption spectroscopy.
Phase fluctuation optical heterodyne spectroscopy is employed to obtain the first nonextractive data on size-mass distribution of submicrometer ammonium sulfate aerosols. The required theory of aerosol absorption of electromagnetic energy and subsequent thermalization is presented. Based on this theory, the predicted behavior was confirmed by experiments using IR absorption of ammonium sulfate aerosols. The results show good agreement with measurements using conventional methods including condensation nuclei counter, electron micrography, and filtration. In addition, a conversion constant for the photothermal signal of ammonium sulfate aerosols is calculated to be 2.3 microV/(microg/m3). Furthermore, the signal is shown to be linear in excitation energy and modulation frequency and scalable.
Fluckiger
D U
DU
Brookhaven National Laboratory, Environmental Chemistry Division, Department of Applied Science, Upton, New York 11973, USA.
Lin
H B
HB
Marlow
W H
WH