where A is the collision cross-section area, 𝐴 4𝜋𝑠 2 is the fraction of the error function that is responsible for hitting as if the target molecule is relatively placed on the shell opening a hole with this area fraction (Fig. ); CB is the number concentration of molecule B with unit # molecule/m 3 , 𝑐 𝐵 4𝜋𝑠 2 𝑑𝑠 is the number of B molecules in the shell that is relatively placed at the center changing the amplitude of the PDF (Fig. ); in the error function part, the integrated fraction in Equation 9, the radial PDF pr mirrors the Maxwell-Boltzmann distribution over a spherical space (Fig. ).