AVS 56th International Symposium & Exhibition
    Surface Science Wednesday Sessions
       Session SS1-WeA

Paper SS1-WeA1
Towards Understanding the Formation of Water in the Interstellar Medium

Wednesday, November 11, 2009, 2:00 pm, Room M

Session: Water/Surface Interactions & Environmental Chemistry II
Presenter: V.L. Frankland, Heriot-Watt University, UK
Authors: V.L. Frankland, Heriot-Watt University, UK
M.P. Collings, Heriot-Watt University, UK
M.R.S. McCoustra, Heriot-Watt University, UK
Correspondent: Click to Email
Exposed to the harsh radiation fields of interstellar space, few molecules can escape photodestruction. However, the vast clouds of gas and dust that accumulate in the gulfs of space between the stars (known as the interstellar medium) have been observed to contain more than 120 different molecular species1. The low temperature (10-100 K) and pressure (10-14 mbar) conditions within the interstellar medium limit the range of viable gas-phase reactions resulting in the gas-phase chemistry alone being insufficient to explain the observed abundances of some key chemical species (for example, H2 and H2O). Dust grains provide a surface on which adsorbed species can react2 and hence an alternative pathway to key interstellar molecules. Indeed, this has been proven for the efficient formation of H2 both experimentally3-6 and computationally7-9.
Surface chemistry within an ultrahigh vacuum chamber is being used to explore the surface irradiation reactions of O on a range of astrophysically relevant surfaces using atomic beam methods. In these experiments, the products are identified using temperature programmed desorption. The results of the experiments are interpreted using kinetic analysis of a simple surface mechanism. Analogous experiments will be conducted using an atomic H beam. The ultimate aim of this research will be to combine the two beams to study in situ H2O formation on a grain surface.
References
1) from “129 reported interstellar and circumstellar molecules” http://www.cv.nrao.edu/%7Eawootten/allmols.html [http://www.cv.nrao.edu/~awootten/allmols.html] (assessed 7th May 2009 )
2) R. Gould, E.Salpeter, Astrophys. J., 1963, 138, 393
3) G. Vidali, J. Roser, G. Manico, V. Pirronello, Adv. Spa. Res., 2004, 33, 6
4) L. Hornekaer, A. Baurichter, V. Petrunin, A. Luntz, B. Kay, A. Al-Halabi, J. Chem. Phys., 2005, 122, 124701
5) F. Dulieu, L. Amiaud, S. Baouche, A. Momeni, J. Fillion, J. Lemaire, Chem. Phys. Lett., 2005, 404, 187
6) J. Perry, J. Gingell, K. Newson, J. To, J. Watanabe, S. Price, Meas. Sci. Technol., 2002, 13, 1414
7) O. Biham, A. Lipshtat, Phys. Rev. E, 2002, 66, 56103
8) N. Katz, I. Furman, O. Biham, V. Pirronello, G. Vidali, Astrophys. J., 1999, 522, 305
9) H. Cuppen, E. Herbst, Mon. Not. Roy. Astron. Soc., 2005, 361, 565