TOF-SIMS investigation of interactions between water and nitrogen at 15 K

TOF-SIMS is used to characterize the van der Waals complex formed on the surface by adsorption of H2O on N-2 molecules. For N-2 adsorption on the amorphous solid water, the H+ yield sputtered from H2O is markedly enhanced with increasing coverage while the H3O+ yield decays monotonically. This is because the H+ ion is created efficiently during collisions between H2O and N-2 molecules. This occurs provided that the N-2 layer (<1 ML) wets the H2O surface and no thick N-2 layer grows on the H2O layer. In the case of amorphous solid water prepared at 15 K, the N-2 molecules are incorporated in the inner pores preferentially and then cover the outermost surface after saturation, suggesting the high mobility of the N-2 molecule on the water surface. A pure H2O film is hardly grown on the N-2 layer (50 ML) up to the H2O coverage of 100-150 ML due to intermixing. (C) 2004 Elsevier B.V. All rights reserved.