Inaug.-diss.--Bonn. / Lebenslauf.

Th.--Sci. phys.--Nancy--I.N.P.L., 1983.

No description available.

[No abstract available] / Science, Faculty of / Physics and Astronomy, Department of / Graduate

[No abstract available] / Science, Faculty of / Chemistry, Department of / Graduate

[No abstract available] / Science, Faculty of / Physics and Astronomy, Department of / Graduate

An automatic calibration marker and wavelength scanning drive has been installed on the Perkin-Elmer infrared spectrometer and the precision of this drive was checked under various operating conditions. The optimum reproducibility was found to be 0.03 wave-drive divisions and the reproducibility under normal operating conditions was found to be G.23 wave-drive divisions at the slowest scanning speed, which is six minutes per revolution of the wave-drive drum. The spectrum of nitrogen dioxide has been examined in the NaCl and LiF prism regions and a tentative assignment of the absorption bands has been made. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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