Effects of target anisotropy on harmonic measure and mean first-passage time

In this paper, we investigate the influence of target anisotropy on two characteristics of diffusion-controlled reactions: harmonic measure density and mean first-passage time. First, we compute the volume-averaged harmonic measure density on prolate and oblate spheroidal targets inside a confining domain in three dimensions. This allows us to quantify the uniformity of this density in the small target limit. Second, we derive an explicit expression of the mean first-passage time to such targets and analyze the effect of anisotropy. In particular, we illustrate the accuracy of the capacitance approximation for small targets.