Collision theory
From Glossary of Meteorology
collision theory
Theory of chemical reactivity that states that only colliding molecules can undergo chemical reaction and then only if their combined kinetic energy exceeds a critical value.
The maximum value for the rate coefficient for a simple, bimolecular, gas-phase reaction, assuming reaction occurs on every collision, is about 2 × 10−10 cm3 per molecule per second. Actual rate coefficients are lower due to two effects—the need to overcome an energy barrier during collision in order for reaction to occur, and a “steric factor,” which accounts for the fact that reaction can occur only when the collision occurs in a certain geometry.
