Plot of anthracene monomer signal σ_an as a function of nominal anthracene density (as calculated from the anthracene flow rate, mixing ratio, and total flow density) in a uniform flow at 60 K. The surviving anthracene fraction (right axis) is calculated by a simple nucleation kinetics model for the reaction time of 73 μs (in red). The gray zone identifies the initial density of anthracene at which the kinetics measurements are performed.