Infrared laser wavelength dependence of particles ablated from glycerol

Particles were generated from glycerol that was irradiated at atmospheric pressure using a mid-infrared optical parametric oscillator at wavelengths between 2.6 and 3.8 μm. The size distribution and quantity of ejected particles with diameters larger than 300 nm were measured using an aerodynamic particle sizer. At a given fluence, the particle concentration roughly tracked the infrared absorption spectrum of liquid glycerol. The threshold fluence for particle formation varied between 1000 and 5000 J/m2 throughout the measured wavelength range and the minimum fluence corresponds to the IR absorption maxima of glycerol. The mean particle size roughly tracks the inverse of the IR absorption and smaller particles are observed at the greatest IR absorption. The material ejection mechanism is interpreted as an explosive boiling process in the stress confinement regime.