Liquids : a molecular hydrodynamics perspective.
New insights into the kinetic and molecular dynamics of liquids are presented through
two distinct experimental studies.
The kinetics and dynamics of cold 12 molecules scattered off liquid polydimethylsiloxane
are studied. Time resolved LIF spectra give number densities and quantum state populations
throughout both the inelastic scattering and the trapping/ desorption processes. The
vibrational cooling of inelastically scattered molecules indicates different mechanisms for
the trapping and desorption processes. Surface temperature dependence yields desorption
enthalpy 23 - 30 kJ moZ-1 and frequency factor 108 - 1010 Hz, thus suggesting predesorption
diffusion. Dynamical behaviour indicates more than one mechanism for activation
of trapped species, i.e., conversion of internal energy into translation and energising via
interaction with liquid molecules.
The molecular dynamics of vertical liquid jets produced by slit nozzles was determined.
The alignment of rhodamine 6G molecules, seeded in ethylene glycol jets, is evaluated
through polarised laser induced fluorescence (PLF). Computational fitting and integration
produce the corresponding liquid velocity distributions. Different streams within the jets
are identified. The study is extended to the alignment inside the nozzle. An asymmetric
nozzle flow is studied in order to verify the conclusions drawn. An interpretation of the
lobed jet kinetics and molecular dynamics is proposed by relating the velocity distributions
with the jet horizontal sections.