Introduction

In 1956 in a classic experiment Ehrlich and Hickmott determined the evolution of the pressure of N₂ evolved from a tungsten filament with time, measured by an ionization gauge, revealing the presence of several kinetic routes for desorption with different energetics [1.1]. Shortly thereafter Redhead extended this method to a continuously pumped volume, yielding pressure bursts which were the derivatives of the pressure buildup curves of the method of Ehrlich and Hickmott and from which activation energies and preexponential factors could be easily estimated [1.2].