Infrared absorption spectroscopy of single particles using photophoresis.
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 CO(2) 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 microm in diameter, the photophoretic force was observed to be negative.
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