Observation of Undercooling in a Levitated Nanoscale Liquid Au Droplet

We investigate melting and undercooling in nanoscale (radius similar to 100 nm) gold particles that are levitated in a quadrupole ion (Paul) trap in a high vacuum environment. The particle is heated via laser illumination and probed using two main methods. First, measurements of its mass are used to determine the evaporation rate during illumination and infer the temperature of the particle. Second, direct optical measurements show that the light scattered from the particle is significantly different in its liquid and solid phases. The particle is repeatedly heated across its melting transition, and the dependence of heating behavior on particle size is investigated. Undercooling-the persistence of a liquid state below the melting temperature-is induced via multistage laser pulses. The extent of undercooling is explored and compared to theoretical predictions.

Automated summary

In this study, melting and undercooling in nanoscale gold particles were investigated in a high vacuum environment. The temperature and state changes of the particles were detected and inferred through measurements of mass and direct optical measurements. The study also found a correlation between heating behavior and particle size. Undercooling, achieved through multistage laser pulses, was explored and compared to theoretical predictions.