6 research outputs found
Extracting the Pair Distribution Function of Liquids and Liquid-Vapor Surfaces by Grazing Incidence X-ray Diffraction Mode
We show that the structure factor of water can be obtained from X-ray
synchrotron experiments at grazing angle of incidence (in reflection mode) by
using a liquid surface diffractometer. The corrections used to obtain
self-consistently are described. Applying these corrections to scans at
different incident beam angles (above the critical angle) collapses the
measured intensities into a single master curve, without fitting parameters,
which within a scale factor yields . Performing the measurements below
the critical angle for total reflectivity yields the structure factor of the
top most layers of the water/vapor interface. Our results indicate water
restructuring at the vapor/water interface. We also introduce a new approach to
extract , the pair distribution function (PDF), by expressing the PDF as
a linear sum of Error functions whose parameters are refined by applying a
non-linear least square fit method. This approach enables a straightforward
determination of the inherent uncertainties in the PDF. Implications of our
results to previously measured and theoretical predictions of the PDF are also
discussed
A Simple Theory of Condensation
A simple assumption of an emergence in gas of small atomic clusters
consisting of particles each, leads to a phase separation (first order
transition). It reveals itself by an emergence of ``forbidden'' density range
starting at a certain temperature. Defining this latter value as the critical
temperature predicts existence of an interval with anomalous heat capacity
behaviour . The value suggested in literature
yields the heat capacity exponent .Comment: 9 pages, 1 figur