Temperature programmed desorption

In the temperature programmed desorption (TPD) technique the shift in equilibium with temperature is used to determine the activation energy for desorption. This activation energy is interesting by itself and can usually be used with other experimental data to calculate the energy of adsorption.

The principle [1, 2] in TPD is that the surface is cleaned and then exposed to a gas at a relatively low temperature. When the desired coverage has been reached, the pressure is reduced, the temperature is increased linearily and the flux of desorbing molecules is measured.

When the surface is heated in a vacuum and K₁, k₂ and K₂ have Arrhenius form equation ? becomes

The equations ? are usually integrated using e.g a Runge-Kutta algorithm. The parameters are T₀, , A and in addition to the initial value _A*. Actually much more complicated sequences of reactions can be simulated in this fashion [3, 4, 5]