Laboratory for Atomic and Surface Physics

Research > Chemical Physics

We study the chemical-physical properties of condensed gases at low temperatures, such as sublimation, phase transformations, mixing, de-mixing, porosity, etc.

Properties of low temperature water ice

Water ice is a common material in the icy satellites of the giant planets, in comets, rings, and ice mantles in interstellar grains.  The properties of ice at the low temperatures of these bodies are very interesting but differ from those of the common, and well studied hexagonal ice.  Experiments at our laboratory found new effects in the sublimation of water ice films at temperatures. The rate of sublimation varies with time as amorphous ice is converted to crystalline ice. We found that the proportion of amorphous ice in the films depends on growth temperature (see Phys. Rev. B 48, 9973 (1993)). We discovered that the porosity of low temperature ice depends on the condition of growth from the gas phase (see J. Chem. Phys. 108 (1998) 3321), which explains the vast range of results reported by different researchers. A review of properties of low temperature water ice and its applications in astrophysics was published in Planet. Sp. Sci . 51, 953-961 (2003).
Properties of solid mixtures of water and hydrogen peroxide

We demonstrated a new method of growing pure hydrogen peroxide in ultrahigh vacuum and apply it to determine thermal stability of the dihydrate compound that forms when water and hydrogen peroxide are mixed at low temperatures. Using infrared spectroscopy and thermo gravimetric analysis, we quantified the isothermal decomposition of the metastable dihydrate at 151.6 K. This decomposition occurs by fractional distillation through the preferential sublimation of water, which leads to the formation of pure hydrogen peroxide. The results imply that in an astronomical environment where condensed mixtures of H2O2 and H2O are shielded from radiolytic decomposition and warmed to temperatures where sublimation is significant, highly concentrated or even pure hydrogen peroxide may form. See J. Phys. Chem. A 115, 5324 (2011)

iR spectra of thermal evolution of ice mixture