Seminars Archive
Infrared spectroscopy of small and large water clusters
Abstract
Wednesday, March 3, 2004, 16:30
Seminar Room, ground floor, Building "T"
Sincrotrone Trieste, Basovizza
Infrared spectroscopy of small and large water clusters
Udo Buck
( Max-Planck-Institut fuer Stroemungsforschung )
Abstract
The investigation of water clusters is considered to be of basic importance
towards the under-standing of the complex properties of bulk water
and
ice from a molecular level. Clusters al-low us to study their properties
as
function of their size and they are also simpler to be treated theoretically.
We apply the vibrational spectroscopy of the OH-stretch mode which
is
quite sensitive to the strength and the coordination of the hydrogen
bonded network. We will present results for small water clusters in
the
range from n=6 to 10 by depletion spec-troscopy which are completely
size selected by the deflection method. The dominant struc-ture found
in this size range is the octamer cube. The signature of solid- and
liquid-like be-havior is discussed in the light of isomeric transitions.
Large water clusters in the size range from tens to thousands molecules
are measured by photo-fragment spectroscopy. Reliable size distributions
are obtained by doping the clusters with one sodium atom and subsequent
photoionization with a single photon. By comparison with calculations
the
measured spectra turned out to be mainly sensitive to the surface.
They exhibit the signature of complete amor-phous behavior up to n
= 300.
Larger clusters start to get a crystalline core but the surface stays
to be amorphous.
Finally we will discuss new schemes for complete size selected large
clusters and
present first results for sodium doped water clusters.
