Collision frequency

Main article: Collision theory

Collision frequency is defined in chemical kinetics, in the background of theoretical kinetics, as the average number of collisions between reacting molecules per unit of time. Its symbol is Z.

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Unlike the preexponential factor, A, which is an empirical magnitude, Z is a theoretical magnitude, calculated ab initio. The closer A and Z are, the better a given theory of chemical kinetics is.

For a gas phase bimolecular reaction Z is

• N_A is Avogadro's number
• σ_AB is the reaction cross section
• k_B is Boltzmann constant
• μ_aB is the reduced mass of the reactants

References

• IUPAC Goldbook definition of Collision Frequency