Photostimulated chemistry at the metal-adsorbate interface

The ultraviolet photochemistry of molecules adsorbed on metallic surfaces has been studied using excimer lasers as radiation source. Dissociation with the fragments either ejected into the gas phase or retained on the surface is one prominent channel. The other is photodesorption of intact molecules. The desorbing molecules are characterized by time-of-flight mass spectroscopy and laser spectroscopy. The state of the adsorbate after irradiation is characterized by thermal desorption spectroscopy and high resolution electron energy loss spectroscopy. The methods and fundamental characteristics are exemplified using results from three studied systems: O₂, H₂O, and N₂O₄ adsorbed on Pd(111).