Laboratory measurement of the pH profile near a vapor-water interface

We have begun a novel set of experiments to observe the pH profile near the vapor-water and vapor-ice interface as a function of growth and sublimation rate and, in the case of ice, also as a function of surface morphology. The temperature and humidity controlled sample is held in a optical cryostat while the ion concentration is measured as a function of depth into the sample using a confocal microscope. Ion concentrations are determined from a combination of Raman spectroscopy and UV fluorescence spectroscopy using a specialized molecular probe whose fluorescence spectrum depends on pH. Initial results for the pH profile near a vapor-water interface will be shown.