AVS 47th International Symposium
    Surface Science Tuesday Sessions
       Session SS3-TuA

Paper SS3-TuA7
From Gases to Dust: Ice Chemistry in the Interstellar Environment

Tuesday, October 3, 2000, 4:00 pm, Room 210

Session: Water/Surface Interactions
Presenter: H.J. Fraser, University of Nottingham, UK
Authors: H.J. Fraser, University of Nottingham, UK
M.R.S. McCoustra, University of Nottingham, UK
D.A. Williams, University College London, UK
Correspondent: Click to Email
It has become clear in the last decade that gas-phase reaction schemes cannot soley account for the variety and richness of chemistry in the Interstellar Medium (ISM). In such environments, gas-dust interactions play a key role. In dense molecular regions, H@sub 2@O is the most abundant ice: it is vital to understand the freeze out, reactivity and desorption processes of atomic and molecular species on such ice surfaces to fully evaluate the chemical evolution of the ISM. A novel surface science experiment has been constructed that simulates the harsh conditions in the ISM. Traditional surface science techniques such as TPD and RAIRS have been combined with a Quartz Crystal Microbalance sample stage, capable of operating below 10 K. The experiment is equipped to study several aspects of the gas-dust interaction that are central to astrophysics, measuring sticking probabilities and rates of desorption empirically and accurately, as well as identifying the nature of the surface bound states. We will present the first results from this experiment, characterising a number of thin molecular ice films prepared under a variety of conditions to reflect a range of substrate morphologies. We will report measurements of the interaction of simple molecular species with these H@sub 2@O ices, concentrating on the behaviour of such systems between 10 and 150 K. The implications of these results to the chemistry and astrophysics of the ISM will be mentioned.