This thesis concerns the study of state-specific collision-induced energy transfer processes between the SiF C<SUP>2</SUP> Δ and <I>B<SUP>2</SUP></I>Σ<SUP>+ </SUP>and the analogous SiC1 <I>B'<SUP>2</SUP> </I>Σ<SUP>+</SUP> states. Laser excitation spectra established the wavelengths at which the SiF <I>B<SUP>2</SUP></I>Σ<SUP>+</SUP> (v' = 0,1,2,4 and 5) and C<SUP>2</SUP> 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 H<SUB>2</SUB>, N<SUB>2</SUB>, CH<SUB>4</SUB> and CO<SUB>2</SUB>, 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 <I>B<SUP>2</SUP></I> Σ<SUP>+</SUP> state except for CO<SUB>2</SUB> 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.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:663523 |
| Date | January 1995 |
| Creators | Watson, Cameron William |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14646 |
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