Thionylimide, HNSO, was prepared and its ultraviolet spectrum recorded for the first time. Two transitions are seen; a long series of bands in the 2700Å region and a continuum ending at approximately 3440Å. Franck-Condon overlap calculations were carried out to ascertain how large a shape change was occurring in the 2700Å system. Reasons for the diffuse nature of the bands in the 2700Å system and the continuous nature of the absorption in the 3440Å region are given. In the second part of this thesis, formulae for the rotational energies of linear polyatomic molecules in ²Σ and ³Σ electronic states in which one or more quanta of a degenerate bending vibration are excited are derived. It is found in ²Σ electronic states that the spin doubling and the ℓ-type doubling are independent provided the rotational constant B is much larger than γ, the spin rotation constant. In ³Σ electronic states departures from the normal triplet spin pattern occur at low N values, when the vibrational angular momentum is still mainly coupled to the axis of the molecule. The effect is enhanced if λ, the spin-spin interaction constant, is large compared to B. At high N values the normal triplet pattern is approached as the vibrational angular momentum is uncoupled from the axis of the molecule. / Science, Faculty of / Chemistry, Department of / Graduate