Extreme Diffusion 2: Experimental Test of a New Model for the Statistics of Extreme Particles in Diffusion

In diffusive environments, the classical model of diffusion well describes the bulk behavior of particles, based on individual particles undergoing independent random walks. However, we should expect that particles near one another should be influenced by the shared medium in which they move. Thus, the distributions of outlier particle locations and first passage times should differ from those predicted by the classical diffusion model. Numerical work has already shown that a shared biasing environment will result in markedly different variance for the location and time of first passage for extreme particles. Here, we probe this by studying first passage times in two different diffusive systems. The first system consists of micron-sized colloids diffusing in water, the second of photons diffusing through a scattering medium. We report on the design of experimental apparati as well as the first measurements of the statistics of extreme particles.