An automated method of determining the relative line separations on digitized blended stellar spectra has been developed. A pair of standard profiles are fitted to the observed blended profile by allowing the standards to relax in position and amplitude until a least-square 'best fit' is obtained. The technique has been tested on numerous blends of known separation and it has been shown that with certain restrictions on the relative amplitudes it is not susceptible to systematic errors. Blended hydrogen and helium lines in two B-stars have been separated to < 100 km/sec at 30 A/mm with a probable error of 15 km/sec. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Flash photolysis of AH₃ (where A = P, As or Sb) produces metastable A atoms in the ²D° and ²P° states, AH, AH₂ and A₂. Similar transients were also observed from ACl₃ with the exception of Sb₂ from SbCl₃. The reaction forming A₂ is probably: 2AH(2ACl) + A₂ + H₂(Cl₂) Since this reaction is endothermic for SbCl no Sb₂ is observed following photolysis of SbCl₃. From the photolysis of PCl₃ a new spectrum was observed and attributed to PCI (³π ← ³Σ⁻). The bands resulting from this transition each consist of three subbands which are easily recognized since the spin-orbit splitting is less than the vibrational spacings in the ³π state. The ΔG₁/₂ value for the ³Σ⁻ ground state is significantly larger than that reported by Basco and Yee⁽¹⁶⁾ from a long wavelength spectrum assigned to PCI. This system may arise by absorption from the metastable ¹Δ state which has the same electronic configuration as the ground state. Spectra of the mixed Group V diatomics AsP, PSb and AsSb were obtained by flashing corresponding mixtures of AH₃ plus BH₃ They are formed by: AH + BH → AB + H₂ AsP was also formed from the mixture of AsCl₃ and PCl₃. That neither PSb nor AsSb were produced from the corresponding chlorides is due to the probable endothermicity for the reaction. The spectrum of AsP consists of a number of strong red degraded bands between 2030 Å and 2260 Å. Due to perturbations a vibrational analysis was not possible. A system of bands in the region of 3000 Å to 3225 Å attributed to AsP by Yee and Joness⁽²⁶⁾ was not detected. Two systems of red degraded bands are attributed to PSb. System 1 (3740 Å -3690 Å) has also been observed by Yee, Jones and Kopp⁽²⁷⁾. System 2 (2420 Å - 2640 Å) is much stronger than system 1. Again, as for AsP, strong perturbations prevented a vibrational analysis. A group of red degraded bands in the region of 3710 Å to 3525 Å were attributed to AsSb. This spectrum was also observed by Yee and Jones⁽²⁸⁾. A vibrational analysis gave ωe and ωexe values of 274.3 cm⁻¹ and 1.7 cm⁻¹ for the upper state. / Science, Faculty of / Chemistry, Department of / Graduate

This thesis examines the collision induced, far-infrared absorption of homonuclear diatomic molecules. These molecular processes are relevant in the astrophysical environments of planetary atmospheres and galactic molecular clouds, and a brief survey of far-infrared measurements of these regions is presented. The theory of collision induced absorption by molecular rotational transitions is reviewed and a calculation is made of the quadrupolar induced, single rotational transition absorption line intensities of the nitrogen and oxygen molecules. The far-infrared absorption spectra of liquid nitrogen and liquid oxygen at 77K, over the frequency range 5 to 70 cm⁻¹ , have been measured. The far-infrared spectrum of liquid oxygen has not previously been reported. The present work includes the design of a low temperature, multiple pass, far-infrared absorption cell intended for low temperature, low density gas measurements. The effect of diffraction on the cell's maximum attainable optical path length, and a model used to estimate the anticipated liquid helium consumption are discussed. / Science, Faculty of / Physics and Astronomy, 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

Stark broadened He I 3965 (4P-2S) has been studied experimentally using a plasma jet as a source. Integrated intensity profiles were obtained by scanning the cylindrically symmetric plasma across its width and using a spectrometer and optical multichannel analyser coupled to a magnetic tape drive system to record the profiles. The resulting data was converted to spectral line shapes as a function of plasma radius through the use of an Abel unfolding procedure carried out by a computer program. The radial dependence of the plasma temperature and density was determined and then used to match experimentally determined profiles with theoretical profiles which take the two forbidden components of the Stark broadened levels into account. Comparison of the experimental and theoretical profiles yielded good agreement. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Several electronic transitions of NO₂, SO₂, and CS₂ have been photographed, and the rotational structures of some of the bands have been analysed. In the spectrum of CS₂, large numbers of 'hot' bands in the first electronic absorption systems of ¹²CS₂ and ¹³CS₂ (3400-4100 A) have been analysed from high-dispersion plates, and accurate rotational constants have been obtained for the overtones of the ground state bending vibration up to v₂ = 6 and ℓ = 3 for ¹²CS₂ and v₂= 4, ℓ = 2 for ¹³CS₂. The energy differences between the various levels with the same ℓ value have been determined to an accuracy of about ±0.006 cm⁻¹ but (because of the parallel polarization of the electronic transition) the absolute energies of levels with ℓ > 0 could not be obtained from these spectra. A detailed rotational analysis of the (0,0) band of the 2²B₂- X²A₁ electronic transition of N0₂, at 2491 A, has been carried out. Although the lines are broadened as a result of predissociation, it has been possible to determine the five quartic centrifugal distortion constants and the spin-rotation coupling constant εaa for the upper ν₃' state. The centrifugal distortion constants allow the position of the unseen vibrational level ν₃' to be estimated : the results offer no support to the suggestion of Coon, Cesani and Huberman that there is a double minimum potential function in the antisymmetric stretching coordinate of the ²B₂ state. The geometrical structure of the zero-poi level of the ²B₂ state is r(N - 0) = 1.314₂ A, ∠0N0 = 120.8₇°, and its lifetime (as calculated from the linewidths) is 42 ± 5 picoseconds. About 160 rotational lines in the region 7370 - 7410 A in the electronic spectrum of NO₂ have been assigned. The lines form the K = 0, 1, and 2 sub-bands of a perturbed parallel band where the upper state A constant is about 17 cm⁻¹. In a diabatic representation, the band can be considered to be a transition within the ground state manifold, which obtains its intensity by vibrational momentum coupling from a nearby band of the A²B₂-X²A₁ electronic transition; its d assignment is 2 13 1-000. Comparison with the spectrum of ¹⁵N0₂ shows that the nearby A₂B₂ level has quite a small amount of vibrational energy, which is not inconsistent with the assignment by Brand, Chan, and Hardwick that the (0,0) band of the A - X transition is at 8350 A. The implications of the electron spin-rotation parameters and the intensity of the 7390 A band are discussed. Rotational analyses have been carried out for the (0,0) bands of the ã³B₁-X¹A₁ absorption systems of S¹⁶0₂ and S¹⁸0₂, from high dispersion plates taken with the gases at dry ice temperature. The rotational analysis of the (0,0) band of S¹⁶0₂ given by Brand, Jones and di Lauro is confirmed in-general, but their values for the anisotropic spin fine structure constants are found to be in error. Our new values remove the discrepancy in the sign of the spin-spin interaction parameter β=E between the gas phase work and the solid state value given by Tinti. This discrepancy had been rationalized by Brand, Jones and Di Lauro in terms of a different choice of phases for the angular momentum operators, but this argument is shown to be incorrect. The spectrum of S¹⁸0₂ confirms our new values for the spin constants in detail. The C¹B₂-X¹A₁ absorption spectra of S¹⁶0₂ and S¹⁸0₂ between 2350 and 2270 A have been analysed in detail from high dispersion plates taken with the gases at dry ice temperature. The centrifugal distortion constants for the (0,0) band are found to disagree with those reported by Brand, Chiu, Hoy and Bist; rotational constants for the other members of the ν₂' progression are given to high precision. Effective constants for the C¹B₂ state of S¹⁸0₂ are reported. Irregularities due to Coriolis coupling observed in the 002 levels of both isotopic species have' been deperturbed to giventhe rotational constants of the unseen 011 levels. A similar deperturbation of the levels 012 and 100 of S¹⁶0₂ has been used to give the rotational constants of the unseen 021 level of the C¹B₂ state. The spectroscopically determined Coriolis and anharmonic coupling constants are reported. An estimate of the energy of the unseen 001 level from the band origins observed gives 236 and 234 cm⁻¹ for S¹⁶0₂ and S¹⁸0₂, respectively. The large anharmonicity observed in the ν₃' manifold confirms the double minimum potential in Q₃ suggested by Brand, Chiu, Hoy and Bist, but indicates that the barrier height is smaller than the value of 100 cm⁻¹ that they report. A detailed theoretical analysis of the direct spin-orbit interaction between electronic states of the same spin multiplicity has been carried out. / Science, Faculty of / Chemistry, Department of / Graduate

Electron impact and electron spectroscopic techniques provide many useful tools for the examination of the physical structure of matter. One of these tools is electron energy loss spectroscopy (EELS). This thesis describes the application of EELS to studies of excitations of the inner-shell electrons of gaseous molecules. Preliminary, low resolution studies in the Department of Chemistry at UBC by G.B. Wight have demonstrated that the technique is experimentally feasible and that many interesting spectroscopic features occur in the inner-shell electron energy loss spectra (ISEELS) of molecules. The present work builds on this foundation and has provided significant extensions not only of the technique but also of its application. Improvements in the experimental apparatus have led to higher energy resolution and more flexible scanning arrangements. The molecular I SEE L spectra of several series of related molecules have been studied including investigations of all observable inner-shell excitation structure between 50 and 700 eV in the simplest saturated, unsaturated and aromatic hydrocarbons (CH₄, C₂H₆, C₂H₂, C₂H₂ and C₆H₆), the methyl halides (CH₃X, X = F, Cl, Br, I), the monohalobenzenes (C₆H₅X, X = F, Cl, Br, I), the chloromethanes (CHxCl₄-x, x = 0 to 4) and chloroethane. A number of specific investigations have been carried out in order to assist spectral interpretations and to further understand the physical nature of inner-shell excitation phenomena. Isotopic substitution has been used to aid the assignment of the carbon 1s spectra of CH₄ (CD₄) and CH₃Br (CD3Br). The first observation of the gas phase energy loss equivalent of extended X-ray absorption fine structure (EXAFS) is reported in the spectra of CH₂CI₂, CHCI₃ and CCI₄. Molecular electric quadrupole transitions have been identified in the sulphur 2p excitation spectrum of SF₆. The improved experimental resolution has led to observations of vibrational structure in the inner-shell excitation spectra of N₂, CO, C₂H₄ and the methyl halides. In addition to the ISEELS studies, electron-ion coincidence techniques have been used to study the ionic fragmentation following excitation and ionization of a sulphur 2p electron in SF₆. This experiment was performed at the FOM Institute for Atomic and Molecular Physics in Amsterdam. An attempt has been made to evaluate alternate theoretical descriptions of certain characteristic inner-shell excitation features in the light of both the electron-ion coincidence results and ISEELS studies of the chloromethanes and SF₆. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

Jet noise remains one of the most important problems in the aviation industry, and its reduction is sought in the context of both commercial and military aircraft. In this thesis, an investigation of the jet noise is conducted in terms of the effect of temperature and Mach number on low frequency acoustic spectra. A low-order model derived from the generalized acoustic analogy method via a lowrequency asymptotic approach is utilized, where the mean flow and pertinent statistical quantities are obtained from RANS simulations. The study involves a combination of seven acoustic Mach numbers ranging from 0.3 to 1.5 and five temperature ratios (TR) ranging from 1 to 3. The model is calibrated with existing experimental measurements of a Mach 0.9 and TR = 1 jet. The results show that the sound pressure level increases with the increase in Mach number, and decreases with the decrease in temperature ratios.

No description available.