Vibrationally mediated photodissociation of water and water containing complexes: state-to-state dynamics of intra- and inter-molecular collisions

The goal of this thesis is to study the dynamics of elementary physical and
chemical processes such as chemical bond breaking and collisional energy transfer on
quantum state-to-state level. Vibrationally mediated photodissociation of i) state
selected H₂O and HOD monomer molecules and ii) state selected Ar-H₂O and Ar-
HOD weakly bound molecular complexes method is used to study the dynamics of HOH
bond breaking in the quantum state selected species probing both intra and inter
molecular dynamics in the photodissociaiton process. Specifically, selected
rovibrational quantum states are prepared in the water molecule second overtone (v_OH
= 3 ← 0) region, followed by the UV photolysis (248 nm) and laser induced
fluorescence characterization of nascent OH or OD rotational, lambda-doublet and
spin-orbit distributions.

This experimental technique is first used to study the dynamics of H-OH bond
breaking in quantum state selected H₂O monomer molecules, probing the influence of
the parent molecule initial state on the observed product state distributions. By the
choice of the photolysis wave length (248 nm) only the exit-channel sections of the
repulsive potential energy surface (PES) are effectively sampled in the experiment.
OH product state distributions resulting from this far off resonance photodissociation
process are compared to similar experiments performed at higher photolysis energies.
Next the vibrationally mediated photodissociation method is extended to study the
dynamics of photodissociation in quantum state selected Ar-H₂O and Ar-HOD van
der Waal complexes prepared in a slit supersonic jet expansion. Comparison between
the cluster (Ar-H₂O or Ar-HOD) and monomer (H₂O or HOD) results explicitly
measures the influence of the intermolecular interaction within the state selected
complex on the UV photolysis dynamics and underscores the dynamical importance
of inelastic itracomplex collisions in the photodissociation event.