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Title: A study of the spectroscopy and collision dynamics of SiX (X = F,C1) radicals
Author: Watson, Cameron William
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1995
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This thesis concerns the study of state-specific collision-induced energy transfer processes between the SiF C2 Δ and B2Σ+ and the analogous SiC1 B'2 Σ+ states. Laser excitation spectra established the wavelengths at which the SiF B2Σ+ (v' = 0,1,2,4 and 5) and C2 Δ (v' = 0,1) levels could be populated selectively. The vibrational transition probabilities of the C - X and B - X systems were measured by observations of the resultant dispersed fluorescence. Comparison with the calculated Franck-Condon factors allowed an assessment of the behaviour of the transition dipole moment functions. The B - X transition moment was essentially invariant with internuclear separation. In contrast, the C - X transition moment was found to be strongly decreasing with increasing internuclear separation. These observations were justified on the basis of simple linear combination of atomic orbitals arguments. The radiative lifetimes of the C and B states were shown to be 94 ± 2 ns and ≤ 10 ns respectively by time resolved measurements of the C - X and B - X decays. Total quenching cross sections for removal of the SiF C (v' = 0,1) state were found to be large for the molecular quenchers H2, N2, CH4 and CO2, although no quenching was observed for Ar and He. A small but quencher dependent fraction of the removed C state molecules was transferred to the B2 Σ+ state except for CO2 as a quencher. The product B state vibrational populations were shown to correlate well with the Franck-Condon overlap between the initial and product vibronic states. The study of the isoelectronic SiC1 transfer system produced results in good agreement with, but of improved precision to those of previous studies. The B' state quenching was efficient for all collision partners with crosssections shown to correlate with long range attractive forces between the collision pair.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available