Measuring electric charging and discharging of individual aerosol particles with optical tweezers

Charge accumulation on aerosol particles, e.g. dust, volcanic ash or cloud ice, plays a critical role in a variety of natural and industrial processes (Zhang et al., 2016). In our experiment, we utilize optical tweezers to levitate individual aerosol particles in the micrometer size range and observe their charging and discharging dynamics over days-to-weeks time periods and with elementary-charge resolution. Using multi-photon absorption from the trapping laser (Ashkin and Dziedzic, 1976) we can charge the trapped particle at different rates and to different values, observing every charging and discharging event along the way. By studying the charge-saturation behavior of the particle and the spontaneous discharges it is undergoing, we hope to contribute to a better understanding of the microphysical processes involved in lightning initiation and adjacent electrical phenomena in the atmosphere.

Zhang L., et al. (2016) Indoor Built Environ 25 (3) 437-440.

Ashkin, A. and Dziedzic, J.M. (1976) Phys. Rev. Lett. 36 (5), 267–270.