Chemisorption decreases with increase in pressure. Why?

Chemisorption is an adsorption which occurs when a gas is held onto the surface of a solid by forces similar to those of a chemical bond.

In chemisorption, the chemical bonds are made by the chemical species with the substrate surface. This process is controlled by the diffusion length of chemical species involved and therefore the pressure of ambient.The rate of chemisorption depends on the flux of chemical species incident on the substrate surface. High incident flux results in high chemisorption rate. As we keep on increasing the pressure, the incident flux gets reduced( due to low diffusion length of species) and hence a decrease in the rate of chemisorption is observed.