In this formula, Collisional Cross Section uses Collision Frequency, Number Density for A Molecules, Number Density for B Molecules, Reduced Mass of Reactants A and B & Temperature in terms of Molecular Dynamics. We can use 1 other way(s) to calculate the same, which is/are as follows -
Collisional Cross Section = pi*((Radius of Molecule A*Radius of Molecule B)^2)