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Compression and caging of CD3Cl by H2O layers on Ru,,001... Y. Lilach and M. Asscher

Summary: Compression and caging of CD3Cl by H2O layers on Ru,,001...
Y. Lilach and M. Asscher
Department of Physical Chemistry and the Farkas Center for Light Induced Processes,
The Hebrew University, Jerusalem 91904, Israel
Received 15 February 2002; accepted 17 July 2002
The interaction of two similar coadsorbed dipolar molecules H2O and CD3Cl has been studied as a
function of coverage over Ru 001 under ultra high vacuum conditions. The complementary
techniques of temperature-programmed desorption mass spectrometry ( P-TPD) and work
function change in a -TPD mode were employed. Adsorption of water on top of CD3Cl reveals
two major trends: At submonolayer methyl chloride coverage, post-deposited water compresses the
methyl chloride molecules and forces them to flip over to the methyl down configuration at the
second layer, leading eventually to three-dimensional islands. This is indicated by both CD3Cl
P-TPD and differential work function d( )/dT data. Higher water coverage (H2O)
1.2 bilayers BL causes full detachment of the CD3Cl molecules from the ruthenium surface, to
be encapsulated within the amorphous solid water ASW layer that is formed. At even higher water
coverage (H2O) 5 BL , methyl chloride desorbs in an explosivelike mode at 165 K. The caged
methyl chloride molecules lack any permanent dipole moment as indicated from differential
-TPD analysis, explained in terms of a high level of disorder within the ASW. The relevance of
the hydrophobic caging process to clathrate-hydrate formation is discussed. 2002 American
Institute of Physics. DOI: 10.1063/1.1505858


Source: Asscher, Micha - Institute of Chemistry, Hebrew University of Jerusalem


Collections: Chemistry