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Title: State-resolved dynamics of electronically inelastic collisions of small free radicals
Author: Randall, Colin James
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1998
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The phenomenon of collision-induced electronic energy transfer in selectively excited diatomic radicals has been investigated experimentally. Direct laser excitation of initial rovibronic states and dispersed, temporally-resolved fluorescence analysis of both parent and collisionally populated levels has allowed the collisional encounter to be quantified at a state-specific level. Theoretical modelling of these results allows the form of the potential energy surfaces which control the dynamics to be established. In an extended series of experiments, collision-induced C2Δ-B2Σ+ transfer in the SiF radical has been investigated. It was observed that the product B2Σ+ state vibrational distributions were well correlated with the Frank-Condon overlap between vibronic wavefunctions of the two states. Dominant channels were found to involve Δv=0, which corresponds to the energy defect of ~5000 cm-1. Rotationally resolved investigation of the C2Δ, v=0→B2Σ+, v'=0 channel revealed a significant fraction of this energy to be released as product state rotation. A limiting impulsive model of the energy release reproduced the main features of the observed behaviour. Polarisation resolved investigation of the transfer event revealed significant depolarisation of the product B2Σ+ state compared to the initial C2Δ state. This observation was rationalised within two dynamically distinct models of rotational energy transfer. It is believed that all these observations may be explained by the valence-Rydberg nature of the electronic states involved. In a related set of experiments, novel measurements of collision-induced transfer between the A2Δ and B2Σ- states of the CH radical have been obtained.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available