Abstract
The preparation of an array of nanocavities (NCs) in silicon via thermal treatments of high-fluence heliumimplantedsilicon is a well established process. The NCs have oered a powerful tool for the preparation of welldefined and ordered internal silicon surface, enabling the experimental investigation of its free energy. Here,instead, we interpret the NCs as an ideal nanolaboratory for the study of the adsorption and desorption of H2on silicon. We will present the determination of the internal pressure through the equilibrium abundances ofmono-hydride dimers and dihydrides obtained with infrared spectroscopy.