Loïc Rondin, Jan Gieseler, Francesco Ricci, Romain Quidant, Christoph Dellago & Lukas Novotny
Understanding the thermally activated escape from a metastable state is at the heart of important phenomena such as the folding dynamics of proteins1,2, the kinetics of chemical reactions3 or the stability of mechanical systems4. In 1940, Kramers calculated escape rates both in the high damping and low damping regimes, and suggested that the rate must have a maximum for intermediate damping5. This phenomenon, today known as the Kramers turnover, has triggered important theoretical and numerical studies6. However, as yet, there is no direct and quantitative experimental verification of this turnover. Using a nanoparticle trapped in a bistable optical potential, we experimentally measure the nanoparticle's transition rates for variable damping and directly resolve the Kramers turnover. Our measurements are in agreement with an analytical model that is free of adjustable parameters. The levitated nanoparticle presented here is a versatile experimental platform for studying and simulating a wide range of stochastic processes and testing theoretical models and predictions.
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