a) Set of TPD curves of 0.2 ML of CH₃CN adsorbed on α-quartz (0001) performed at 3 K min^-1, 6 K min^-1, and 12 K min^-1. Straight lines are the fit of these data using a first order kinetic Polanyi-Wigner law with a distribution of adsorption energy using a prefactor of 10¹⁵ s^-1. b) Search for the best value for the prefactor ν: plot of the standard deviation of the three minimum occupied adsorption energies as extracted from the fits of the three TPD curves. The minimum of the curve give the best choice for ν. c) Adsorption energy distribution corresponding to 0.2 ML of CH₃CN on quartz using the best choice for the prefactor.