Stand-off identification of aerosols using mid-infrared backscattering Fourier-transform spectroscopy.

We show that it is possible to identify the chemical composition of an aerosol by using Fourier-transform spectroscopy of backscattered mid-infrared light at a range of 0.2 m. An ultrafast mid-infrared optical parametric oscillator provides the illumination source for the measurement across a wavelength range from 3.2-3.55 μm containing characteristic optical absorption features for two different chemicals. Normalized detection sensitivity below 10  ppm m^-1 Hz^-1/2 is obtained.