ASSOCIATIVE VERSUS DISSOCIATIVE ADSORPTION OF WATER ON AL(100)

The adsorption of water on Al(100) at 100 K has been studied using Fourier transform infrared-reflection absorption spectroscopy (FTIR-RAS), nuclear reaction analysis (NRA) and work function measurements (DELTAphi). All results are consistent with molecular adsorption, as no evidence was found for other possible dissociation products such as atomic O or D (H) at this temperature. By condensing alternating layers of D2O and H2O, it was found that a narrow feature in the nu(OD) (nu(OH)) region of the spectrum at 2720 cm-1 (3700 cm-1) is associated with non-hydrogen bonded OD (OH) groups in water molecules existing at the ice-vacuum interface. Surface hydroxyl groups resulting from dissociative adsorption exhibit a broader O-D stretch at 2760 cm-1.