Acoustic Levitation as an IR Spectroscopy Sampling Technique

Abstract

Acoustic levitation of liquid droplets (< 4 mm diameter), bubbles, and solid particles is described as an unusual sampling technique for obtaining the infrared spectrum of samples that might be incompatible with conventional sample support methods, and for studies of materials under extreme conditions. Excellent FT-IR spectra were recorded of bubbles of a concentrated aqueous nitrate solution, of mineral oil, and of an aqueous surfactant solution. Polymethacrylic acid packing foam also produced a high-quality spectrum. Large aqueous droplets and dense solids gave unsatisfactory spectra. The design of the levitator and various spectroscopic considerations are discussed.