where D °H2O(T) is the temperature-dependent diffusion coefficient of water in pure water calculated with the Stokes-Einstein equation, and η °H2O(T) is the temperature-dependent viscosity of pure water. η °H2O(T) was calculated, as done previously, using a VFT fit to pure water viscosity data. η(T) is the viscosity in the SOA calculated with the VFT equation, and ξ is the fractional exponent determined by: