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

TitleVibrationally mediated photodissociation of water and water containing complexes: state-to-state dynamics of intra- and inter-molecular collisions
Publication TypeThesis
Year of Publication1999
AuthorsVotava, O
Abstract

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 (vOH = 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.