The Stark field perturbed spectra of near infrared vibrational overtones of hydrogen fluoride and acetylene have been measured with a high resolution molecular beam laser spectrometer. A high performance laser power build-up cavity (optical resonator) was constructed to measured the weak ro-vibrational transitions of the v₂ + 3v₃ vibrational combination band of acetylene. The measured gain of the build-up cavity was found to be at least 300 out of a potential 2000. The primary reason for the lower than expected gain was attributed to losses induced by the extreme heat build-up on the mirror surfaces. The electric dipole moment for the v = 3 vibrational overtone of hydrogen fluoride was determined to be 1.9614 ± 0.0021 Debye. This result was compared with predictions from the available theoretical models and some theoretical constants were revised based on the current contribution to dipole moment function of hydrogen fluoride. The Stark field perturbed spectra of the v₁ + 3v₃ and v₂ + 3v₃ vibrational combination bands of acetylene were analysed for their polarisability tensors. In order to complete the study, the ground electronic state static polarisability and anisotropy of the polarisability were also determined. They were found to be 3.96A³ and 1.071 ± 0.014A³, respectively. The |1030⁰0⁰> state (v₁ + 3v₃) was observed to be coupled with the |0040⁰0⁰> infrared forbidden state (4v₃) in the presence of the Stark electric field. The resultant analysis produced values of 4.62 ± 0.09A³ for the polarisability and 1.15 ± 0.03A³ for the polarisability anisotropy of the |1030⁰0⁰> state. The difference in energy between |1030⁰0⁰> and |0040⁰0⁰> was determined to be 4.133 cm⁻¹, which compares well with local mode calculations. The measurements of the v₂ + 3v₃ band indicated that the |0130⁰0⁰> state was strongly coupled with another infrared allowed, unidentified (rogue), state in the absence of the Stark field as well as with the infrared forbidden, |1120⁰0⁰> state in the presence of the Stark field. The previously unobserved J = 5 ← 4 transition of the infrared allowed rogue state was recorded here for the first time. The Stark field perturbed spectra of the R(3) and R(5) ro-vibrational transitions of the v₂ + 3v₃ band also showed evidence of rogue transitions. The ensuing analysis determined that the |0130°0°) state has a polarisability of 3.5 ± 0.3A³ and a polarisability anisotropy of 5.6 ± 1.8A³. The Stark field perturbed spectra of the R(3) and R(5) transitions were fit to a non-crossing model and the energy levels of the rogue J = 4 and J = 6 states were determined. The energy level difference between |0130°0°) and |1120°0°) was determined to be -11.88±0.22 cm⁻¹. This does not compare well with local mode calculations and it is possible that the perturbations due to the presence of the rogue state impeded the accurate determination of the energy level difference. The identity of the rogue vibrational state could not be determined from the data presented in this thesis alone. However, collaborative work with another research group suggests that the rogue vibrational state is |0306°3¹) (see Chapter 7). / Graduate

The radiation-induced decomposition of glycine is studied using a combination of Near Edge X-ray Absorption Fine Structure (NEXAFS) measurements and density functional theory calculations. Principal Component Analysis was used to determine the number of distinct molecules that were needed to explain the observed changes in the measured spectra, and the emerging absorption features are assigned to various product molecules through comparison with simulated spectra of several model compounds. It is clear from the experiment that the major effect of soft X-ray irradiation is the fragmentation of the molecule, primarily at the carbonyl sites. Peptide formation is shown to occur under irradiation; a condensation reaction initiated by the removal of a carbonyl oxygen is the proposed mechanism. This study utilizes a novel approach to the study of radiation damage that can occur during measurements, and suggests that it may be possible to use simulated model spectra to correct for these effects in measured spectra.<p> A study of oligothiophene-based molecular semiconductor materials with potential applications in light-emitting and photovoltaic devices is undertaken. Angle-resolved NEXAFS measurements of the star-shaped 4(HPBT) molecules on an amorphous indium surface show a strong dichroic signal indicating a well-ordered, uniformly upright arrangement of planar molecules. The X-ray excited optical luminescence (XEOL) measurements showed several sharp features associated with vibronic splitting of the LUMO-HOMO luminescent transition. The HOMO-LUMO gap determined from the XEOL measurements is 2.28 eV; this value is in agreement with previously published optical measurements as well as with the value that is estimated from the combination of NEXAFS and X-ray emission spectroscopy (XES) measurements. Films formed from blended solutions of 4(HPBT) and the hole-transporting molecular semiconductor PCBM are shown to form a bilayer structure with the PCBM adjacent to the substrate. Annealing causes desorption of the 4(HPBT) from the surface.

The radiation-induced decomposition of glycine is studied using a combination of Near Edge X-ray Absorption Fine Structure (NEXAFS) measurements and density functional theory calculations. Principal Component Analysis was used to determine the number of distinct molecules that were needed to explain the observed changes in the measured spectra, and the emerging absorption features are assigned to various product molecules through comparison with simulated spectra of several model compounds. It is clear from the experiment that the major effect of soft X-ray irradiation is the fragmentation of the molecule, primarily at the carbonyl sites. Peptide formation is shown to occur under irradiation; a condensation reaction initiated by the removal of a carbonyl oxygen is the proposed mechanism. This study utilizes a novel approach to the study of radiation damage that can occur during measurements, and suggests that it may be possible to use simulated model spectra to correct for these effects in measured spectra.<p> A study of oligothiophene-based molecular semiconductor materials with potential applications in light-emitting and photovoltaic devices is undertaken. Angle-resolved NEXAFS measurements of the star-shaped 4(HPBT) molecules on an amorphous indium surface show a strong dichroic signal indicating a well-ordered, uniformly upright arrangement of planar molecules. The X-ray excited optical luminescence (XEOL) measurements showed several sharp features associated with vibronic splitting of the LUMO-HOMO luminescent transition. The HOMO-LUMO gap determined from the XEOL measurements is 2.28 eV; this value is in agreement with previously published optical measurements as well as with the value that is estimated from the combination of NEXAFS and X-ray emission spectroscopy (XES) measurements. Films formed from blended solutions of 4(HPBT) and the hole-transporting molecular semiconductor PCBM are shown to form a bilayer structure with the PCBM adjacent to the substrate. Annealing causes desorption of the 4(HPBT) from the surface.

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.

Thesis (PhD)--University of South Australia, 2003.

Thesis (Ph. D.)--Swinburne University of Technology, Centre for Molecular Simulation - 2008. / Dissertation submitted in fulfilment of requirements for the degree Doctor of Philosophy, Centre for Molecular Simulation, Swinburne University of Technology, 2008. Typescript. Includes bibliographical references (p. 188-218).

No description available.

Call number: LD2668 .T4 1984 N43 / Master of Science

No description available.