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

Some unstable gaseous molecules, cobalt oxide (CoO), niobium nitride (NbN) and aminoborane (NH₂BH₂), were studied by high resolution optical spectroscopy. A portion of the "red" system of CoO, from 7000 Å to 5800 Å, was measured using laser induced fluorescence techniques. Three bands of the system, with origins at 6338 Å, 6411 Å and 6436 Å, were rotationally analyzed. The lower levels of these parallel bands are the Ω = 7/2 and 5/2 spin-orbit components of a ⁴∆i electronic state. Available evidence indicates that this is the ground state of the molecule; its bond length is 1.631 Å. This work completes the determination of the ground state symmetries for the entire series of first row diatomic transition metal oxides. The hyperfine structure in the ground state is very small, supporting a σ²δ³π² electron configuration. The upper state, assigned as σδ³π²σ*, has large positive hyperfine splittings that follow a case (aβ) pattern; it is heavily perturbed, both rotationally and vibrationally. The sub-Doppler spectrum of the ³Φ₋³∆ system of NbN was measured by intermodulated fluorescence techniques, and the hyperfine structure analyzed. Second order spin-orbit interactions have shifted the ³Φ₃₋³∆₂ subband 40 cm⁻¹ to the blue of its central first order position. The perturbations to the spin-orbit components were so extensive that five hyperfine constants, rather than three, were required to fit the data to the case (a) Hamiltonian. The ³∆₋³Φ system of NbN is the first instance where this has been observed. The magnetic hyperfine constants indicate that all components of the ³∆ and ³Φ spin orbit manifolds may be affected, though the ³∆ state interacts most strongly, presumably by the coupling of the ³∆₂ component with the ¹∆ state having the same configuration. The Fermi contact interactions in the ³∆ substates are large and positive, consistent with a σ¹δ¹ configuration. In the ³Φ state the (b + c) hyperfine constants are negative, as expected from a π¹δ¹ configuration. The ³∆ and ³Φ bond lengths are 1.6618 Å and 1.6712 Å, respectively, which are intermediate between those of ZrN and MoN. The Fourier transform infrared spectrum of the V7 BH₂ wagging fundamental of NH₂BH₂ was rotationally analyzed. A set of effective rotational and centrifugal distortion constants was determined, but the band shows extensive perturbations by Coriolis interactions with the nearby V5 and V11 fundamentals. A complete analysis could not be made without an analysis of the V5-V7-V11 Coriolis interactions, which is currently not possible because the very small dipole derivative of the V5 vibration has prevented its analysis. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

This work consisted of an experimental investigation of the formic acid (HCOOH) molecule's rotational spectrum. Measurements of line widths were obtained for J = 5, 12, 13, 19, and 20 for a pressure range from 1 to 10 microns. A linear behavior between Av and p was observed as predicted by theory. The line width parameter Avp was observed to depend on the quantum number J. Hard sphere collision diameters b1 were calculated using the obtained AvP values. These deduced hard sphere values were found to be larger than the physical size of the molecule. This result was found to be in general agreement with other investigation in which long range forces (dipole-dipole) dominate.

No description available.

Exact quantum mechanical-vibrational transition probabilities are calculated for a collinear atom-diatomic molecule collision, using the real reactance matrix K. Both the Morse and harmonic binding potentials are considered. It is found that the discrepancy between the transition probabilities for these binding potentials may be large, depending on the collision parameters m and α; the discrepancy increases as m becomes large and decreases as α becomes large. Large Morse well depths (characterised by large values Of De) do not necessarily imply agreement between the transition probabilities of the two oscillators. Anharmonicity will be important in most collisions. The validity of several approximate theories when applied to this problem is investigated, It is found that the revised first order distorted wave approximation of Mies (1964a), and hence the revised first order perturbation theory approximation (Mies 1964b), are valid providing the reduced mass m is not too large or the collision too strong. Based on these investigations the one-dimensional form of the correspondence principle for strongly coupled states (Percival and Richards 1970a) is modified to include, approximately, the perturbation of the bound system. The modified theory is tested on the system of a harmonic oscillator, perturbed by a potential q2F(t) and excellent agreement with the exact quantum mechanical solution is obtained. The theory is then applied to the collinear atom-diatomic molecule collision, with a Morse molecular binding potential. For a large range of collision parameters, the results are in good agreement with the exact quantum mechanical transition probabilities, even for low order transitions. The modified correspondence principle is shown to have a larger range of validity than the revised first order perturbation theory approximation of Mies (1964b)to which it reduces in the weak perturbation limit.

No description available.

Thesis--University of Oulu, 1985. / Includes bibliographical references (p. [21]-22).

Hydrazoic acid has been photolysed in a krypton matrix at 4°K and the products studied by electron spin resonance spectrometry. This study showed that NH₂ radicals have been produced as a secondary product in the reaction. In addition a broad, intense resonance at g = 2 and a weak, half field resonance has been tentatively assigned to the imine (NH) radical. This suggestion is shown to be consistent with theoretical considerations. Diazomethane has also been photolysed in krypton and carbon monoxide matrices at 4°K, and the products studied by e.s.r., in an attempt to detect the methylene (CH₂) radical. The results of this study were complicated and a complete analysis was not possible. It is suggested that some of the features may be explained in terms of an overlap of the spectre from CH₃ and CH radicals. There are difficulties in such an explanation however. A study has been made on the line shapes of poly-crystalline samples of aromatic triplet state molecules. It is shown how the experimentally observed spectra of the photoexcited triplet states of axially symmetric molecules such as triphenylene and non-axially symmetric molecules such as naphthalene and phenanthrene can be explained in terms of a line shape calculated from a first order perturbation treatment. This model gives a good explanation of the observed line shapes, however better agreement with the observed field positions is obtained if a second order correction is included. Line shape calculations have also been made for molecules, such as the substituted imines, where spin-spin interaction is large. It is shown that the calculation is in agreement with the observed spectra of phenylimine and benzenesulfonylimine. In addition, it is shown how the experimentally determined value of the spin-spin interaction constant, D, can be related to the spin density on the nitrogen of the substituted imines. The spin densities calculated in this way are in good agreement with spin densities calculated on the basis of the Hückel theory. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.