Page 12 was not included in the thesis. / <p> This work extends the knowledge about the excited electronic states of thioformaldehyde. Survey work is reported over the wavelength region from 230 nm to 180 nm and four electronic transitions are identified. These are assigned as the 1Al(π,π*), 1B2(n,3s), 1Al(n,3py) and 1B2(n,3pz) systems.</p> <p> A vibrational and rotational analysis of the first two systems has been undertaken. The results of these analyses indicate that the molecule remains planar or nearly so in both the 1Al(π,π*) and the 1B2 (n,3s) transitions. This behaviour is contrasted to that of similar molecules which are known to be non-planar in these electronic states and reasons are offered for this observation. The substituted geometry for thioformaldehyde in the 1B2(n,3s) state has been calculated and provides insight into the changes which occur in the molecule on electronic excitation.</p> / Thesis / Doctor of Philosophy (PhD)

The ¹A₂ ← ¹A₁ (π* ← n) electronic absorption spectrum of thioformaldehyde vapour has been investigated. The six excited state fundamental frequencies for both CH₂S and CD₂S are determined from the vibrational analysis. The three rotation constants and three symmetric top distortion constants for the 0⁰₀, 4¹₀ and 3¹₀4³₀ bands of CH₂S and the 0⁰₀, 4¹₀ and 5¹₀ bands of CD2S are determined from a least squares rotational analysis of these bands. The rotational constants of the 0⁰₀ and 4¹₀ bands of CH₂S and CD₂S are used to determine the structure of the molecule in the excited state. / Thesis / Doctor of Philosophy (PhD)