Photo-stimulated desorption (PSD) is desorption of adsorbed molecules from surfaces induced by photon irradiation. PSD occurs either in thermal or nonthermal ways. In the former case, the energy of light absorbed by solid surfaces is converted to heat, leading to the thermally activated desorption, where the desorbed molecules are in thermal equilibrium with the surface at a certain temperature. In the latter case, on the other hand, the photo-excitation is classified into two regimes, phonon excitation and electronic excitation of the adsorbate-surface complex depending on the photon energy. The absorbed light energy is transferred to the adsorbate through phonon–phonon or electron–phonon interaction, which eventually leads to breaking of the adsorbate-surface bond. In the case of electronic excitation, the excitation is further classified into either core electron or valence electron excitation.
KeywordsElectronic excitation Phonon excitation Potential energy surface Lifetime Laser-induced thermal desorption