Abstract

In situ infrared absorption spectroscopy was performed on a single suspended salt particle using photophoresis. The charged ammonium sulfate particle was levitated in an electric–quadropole field and illuminated by a CO₂ laser. The size-dependent absorption spectrum of ammonium sulfate particles was observed for the first time to our knowledge at 930–1080 cm⁻¹. The effects of gas pressure and laser power were also determined. For particles approximately 10 μm in diameter, the photophoretic force was observed to be negative.

© 1985 Optical Society of America

Photothermal aerosol absorption spectroscopy

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