A novel diagnostic for dust particle size in a low-pressure nanodusty plasma based on the decay of the electron density released by laser-induced photodetachment

One of the key parameters in low-pressure nanodusty plasmas is the dust particle size. In this work, we introduce a new method for the determination of the dust particle size in a nanodusty plasma, created in a mixture of argon and hexamethyldisiloxane. To this end, an ultraviolet ( λ = 266 nm ) pulsed laser was used to release plasma-collected electrons from the nanoparticles. Subsequently, the response of the free electron density of the plasma was measured using microwave cavity resonance spectroscopy. Using a stochastic model for particle charging using orbital-motion limited (OML) theory, the predicted charging timescale can be directly compared to the experimentally measured decay timescale of the photo-released electron density. Good agreement was found between the experimentally predicted dust particle size and ex situ scanning electron microscopy (SEM) measurements. Furthermore, the sensitivity of the OML model to its input parameters was assessed. Finally, reversing the method can yield an estimate for the positive ion density based on the dust particle size from SEM.