Analytical Formula for Calculating Adsorption Density of States on Chamber Surfaces from Measured Pressure Change

Pressure decay during an evacuation process of a vacuum chamber often shows a power-law dependence on time, which is considered to reflect the distribution of the adsorption energy of particles on the surface of the chamber. We derive an analytical formula that directly transforms the pressure change into the adsorption density of states. This method shows that the power-law behavior is equivalent to the situation in which the chamber surface has a constant- or exponential-type adsorption density of states for particles under a quasi-static condition.