Physisorption
Ultra-high vacuum noble gas purification. Purification methods

Physisorption is a reversible process that allows many gaseous species (H₂O, CO₂ , N₂ , CO, C_xH_y, etc.), including noble gases, to be adsorbed by trapping onto the mostly cooled surface of an adsorbent. This is a multi-layer phenomenon in which each adsorbed particle constitutes a potential adsorption site for the next layer (figure 7). The forces binding the adsorbent to the adsorbate remain weak, ranging from 0.5 to 50 kJ · mol^–1, i.e. a tenth of the energy of a covalent bond.