Steric factor

Steric factor ρ is a term used in collision theory.

It is defined as the ratio between the experimental value of the rate constant and the one predicted by collision theory. It can also be defined as the ratio between the preexponential factor and the collision frequency, and it is most often less than unity. Physically, the steric factor can be interpreted as the ratio of the cross section for reactive collisions to the total collision cross section.