STRUCTURE SENSITIVITY IN THE SURFACE-CHEMISTRY OF ICE - ACETONE ADSORPTION ON AMORPHOUS AND CRYSTALLINE ICE FILMS

The adsorption of acetone on ice under ultrahigh vacuum has been inves tigated using temperature-programmed desorption mass spectrometry and single-reflection Fourier transform infrared spectroscopy. Two types o f film were investigated: amorphous ice, which has a high density of f ree surface OH groups, and crystalline ice, on which free OH groups ar e not spectroscopically detected. On the amorphous film, two states of acetone are observed during temperature-programmed desorption, one de rived from acetone which forms a hydrogen bond with the ice surface an d a second which is attributed to the desorption of physisorbed aceton e. Only the physisorbed state is observed during desorption from a cry stalline ice film. This work provides clear and convincing evidence th at the surface properties of amorphous ice are different from those of crystalline ice.