LAUSR

In this study, the effect of externally added hydrogen chloride (HCl) on the crystallization of amorphous solid water (ASW) has been examined. ASW films containing small amounts of HCl, which dissociated into H+ (excess protons) and Cl– ions, and having a thickness of 90–360 monolayers (ML) were prepared on a Pt(111) substrate under an ultrahigh vacuum environment. The location of HCl in the samples was varied by controlling the stacking sequence of H2O and HCl during the film growth. Crystallization kinetics of these samples were examined by conducting temperature-programmed desorption experiments and isothermal kinetic measurements with reflection–absorption infrared spectroscopy for the temperature range of 137–145 K. Crystallization behaviors of pure and NaCl-doped ASW films were also examined for comparison. The results indicated that the excess protons accelerated the crystallization of the ASW films, in contrast to the retardation effect of Na+. In the presence of 0.1 ML HCl, the overall activation...