The strongest features in the absorption spectrum of CS₂ in the region 2900Å to 3500Å are identified, from temperature studies, as a π → π* ¹Δu - ¹Σ⁺g transition, where the Renner-Teller effect has split the ¹Δu state into ¹B₂ and ¹A₂ component states of a bent molecule. Analysis of some of the least severely perturbed bands of the ¹B₂ - ¹Σ⁺g transitions (3300 - 2900Å) shows that they form a parallel-polarized progression in the bending vibration, to an upper state with r(C - S) = 1.54₄Å, < SĈS = 163°, and a barrier to linearity of ~ 1400 cm⁻¹. Two hitherto unrecognized progressions of 'hot' bands, a weak vibronic ∏ - ∏ and a stronger vibronic Δ - Δ progression in the region 3300Å to 3500Å, are assigned to the ¹A₂ - ¹Σ⁺g transiton. This is a new type of transition, which does not appear in cold absorption, but whose 'hot' bands can obtain an amount of intensity (proportional to K²) through Renner-Teller mixing. / Science, Faculty of / Chemistry, Department of / Graduate

The effects arising from quadratic electron-phonon interaction and anharmonicity on the optical spectra of imperfections in nonmetals are examined. The absorption or emission line-shape function is expressed in terms of Kubo's formula and is reduced to a trace over phonon states only via the application of the Barrie-Sharpe method. This trace is evaluated with the aid of quantum field-theoretic techniques. It is shown that both the quadratic electron-phonon interaction and anharmonicity modify the phonon spectrum, and the influence of this modification on the optical spectra is studied in detail with regard to position, intensity, width, Stokes' shift and mirror reflection symmetry. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The introduction of boron into a silicon crystal lattice produces two sets of acceptor impurity states: (i) the "external" states (which include the acceptor ground state) which are associated with the P₃/₂ valence band maxima and are the usual impurity states lying in the forbidden gap, (ii) the "internal" states which are associated with the P₁/₂ valence band maximum and are degenerate with P₃/₂ continuum states. The energies of the transitions from the ground state to the so-called 2p', 3p' and 4p' internal acceptor states are such that the 2p', 3p' and 4p' internal absorption peaks are seen in the infrared. Three different experiments are performed to study the "internal" spectrum of boron-doped silicon. (i) The stress-perturbed behavior of the 2p' and 3p' absorption peaks is studied with the use of calibrated uniaxial stress (≤ 10⁹ dynes/cm² ) and polarized light. From these data it is deduced that the ground state has a ⌈8 symmetry while the 2p' and 3p' internal states each have a ⌈6 symmetry. In addition the deformation potential parameters of the ground state are calculated to be: b' = -0.66 ± 0.04 eV. and d' = -2.1 ± 0.2 eV. These calculated parameters for the ground state are used to obtain indirectly some information about the deformation potential parameters of the P₃/₂ valence band edge. (ii) For the temperature range 5°K ≤ T ≤ 60°K the temperature dependences of the breadths of the 2p' and 3p' peaks are measured. These temperature dependences are attributed to phonon broadening. The phonon broadening mechanism for the 2p' and 3p' peaks is shown to be primarily due to a lifetime effect caused by electron-phonon coupling of the 2p' and 3p' states to the P₃/₂ valence band states. (iii) For the impurity concentration range 2.6 x 10¹⁵ boron/cm³ ≤ N ≤ 4.5 x 10¹⁷ boron/cm³ the 2p' absorption peak is measured. With increasing concentration this peak is observed to broaden and become very asymmetrical. Explanations to the above data are presented. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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Thesis (M.Phil.)--Chinese University of Hong Kong. / Bibliography: leaves 83-84.

The chemistry and dynamics of our atmosphere are complex and diverse. A plethora of different chemical reactions are thought to be important, of which only some are known, and even less are well understood. Many of these atmospheric reactions involve highly reactive or unstable trace species, which can be difficult to study experimentally. However, the advancement of computational methods and hardware now make it possible to investigate these chemical species theoretically to an accuracy that is useful for atmospheric chemistry. In this thesis, we have applied modern electronic structure methods to some prototypical hydrogen bonded complexes and sulfonic acid derivatives to better understand the roles of these trace species in the atmosphere. We have calculated fundamental and overtone vibrational spectra, electronic absorption spectra, and reaction energetics with high level ab initio methods. Where possible, we compare our calculated results to experiment and in the absence of experimental data we suggest that our theoretical findings may be of use to atmospheric modelers.

Thesis (Ph. D.)--University of Michigan, 1923.

Thesis (Ph. D.)--University of Rochester, 1948. / Each part preceded by half-title not included in the foliation (3 leaves). Reproduced from type-written copy. Bibliography: leaves 56-58.

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