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

Charge-transfer complexes of the aromatic hydrocarbon-trinitrobenzene type are stabilized principally by interaction between a dative- and a "no-bond" state: φN= a ψ₀ (DA) + b ψ₁ (D⁺A¯) . The resulting complexes usually possess a colour which is associated with an electronic transition between the ground state φN and a predominantly dative excited state; the transition therefore corresponds to the partial transfer of an electron from the donor (D- usually the hydrocarbon) to the acceptor (A). Most of the previous spectroscopic work on CT complexes has been concerned with solutions of the complexes; no detailed investigation of a crystalline complex has been made. The somewhat random nature of CT interaction in solution tends to limit the amount of information we can gain from such studies, and this has prompted the present work on solid complexes. With a system of definite composition and structure, both the spectroscopic examination and theoretical treatment can be carried out at a more quantitative level. The results of a detailed spectroscopic study of the crystalline anthracene-trinitrobenzene complex are presented. It is shown that 1) The CT transition moment is strongly polarized parallel to the c-axis of the crystal (approximately perpendicular to the molecular planes), with a polarization ratio greater than that predicted by the simple oriented gas model. 2) A portion of the intensity of the CT state is derived from mixing with the more intense ¹La state of anthracene, confirming the prediction of J. Murrell. 3) The crystal emission spectrum consists almost entirely of CT fluorescence with vibrational structure similar to that of the absorption. The entire spectrum is blue-shifted with respect to that of the rigid-glass solution; as in solution, there is a very wide gap between the absorption and fluorescence origins. 4) The emission intensity is strongly temperature dependent; a portion of this dependence is reversible, while the remainder is apparently connected with the creation of crystal defects on cooling, and cannot be reversed. It is suggested that the CT state is highly delocalized in the crystal, and that the transition dipole moment connecting the ground- and CT states must be polarized along the c-axis of the crystal, rather than between the centers of the individual donor-acceptor pairs. A number of TNB complexes of other hydrocarbons were studied, although in much less detail. Their spectroscopic properties appear to be similar to those of anthracene-TNB. Polarized phosphorescence- and triplet-triplet absorption spectra of several aromatic hydrocarbons dissolved in crystalline benzophenone are given. This is the first reported observation of triplet-triplet absorption in crystals, and it is shown that it is polarized mainly in the planes of the molecules investigated. / Science, Faculty of / Chemistry, Department of / Graduate

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

Photographic and Photoelectric measurements were made on the shock excited spectra of Argon and Helium. The plasma temperature and electron density in the region behind the shock wave were calculated from the spectroscopic measurements. These quantities were compared with the values obtained from the Rankine Hugoniot shock theory including the effect of ionization. Considerable disagreement was found between experimental results and theoretical predictions. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The pure rotational spectrum of difluorochloromethane, Freon 22, has been obtained in the K-band microwave region with a Stark modulation spectroscope. Over two hundred spectrum lines, of which the majority are grouped into doublets or quadruplets, have been found. Fifteen doublets and one quadruplet correspond in frequency with previous determinations but the majority of the lines and structures have not previously been recorded. In addition, a definite sestet of lines and two definite triplets have been noted. The grouping into multiplets has been made possible by similarities in the line shape, in the Stark modulation response, and in the effects of chilling the Stark cell with dry ice. The latter effect has been the most important factor in identifying several transitions involving low values of J, the total angular momentum quantum number. The sestet and two quadruplets have been found to be the result of the interaction of the Cl³⁵ quadrupole moment with the electrostatic potential at the site of the nucleus. The sestet represents six of the possible eight lines for a transition from a J=1 rotational level to a J=2 level. The quadruplets represent two transitions involving only J=3 rotational levels. From these three structures have been obtained the complete solution for the spectrum of the molecule containing CI³⁵ and the values of the components of the quadrupole coupling constant for the CI³⁵ nucleus along the principal axes of the angular momentum ellipsoid. In all, eight multiplets have been correctly identified for the molecule containing Cl³⁵ and the two theories of the rotational levels and of the hyperfine structure for an asymmetric top molecule have been verified. From the rotational constants for the molecule containing CI³⁵ the values for the molecule containing CI³⁷ can be closely estimated and the rotational spectrum for the latter case has accordingly been predicted with considerable accuracy. By means of the predicted values, five multiplets and one single line have been identified for the molecule containing CI³⁷ and the theories for the rotational levels and for the hyperfine splittings can be rechecked. From the spectra for the two molecules, five independent rotational constants have been obtained with a precision that compares favourably with the precision of other experimenters in the field of microwave spectroscopy. With these five constants and an approximation to the carbon-hydrogen bond length, the structure of the molecule has been calculated with an accuracy much better than that obtained from electron diffraction measurements. The quadrupole coupling constant for CI³⁵ in Freon 22 has been found to be -71.6 ± 0.5 Mc/s, a value which is about 1 Mc/s larger than the value for the molecule in the solid state. The difference between the components of the quadrupole coupling tensor along two axes perpendicular to the carbon-chlorine bond has been found to be rather small in comparison with the value suggested by bond theory. Some comments are offered on the nature of the chemical bond in the light of these electric quadrupole moments for CI³⁵ and the bond lengths for the carbon-chlorine and carbon-fluorine bonds which have been calculated to be 1.7576 ± .0093 Å and 1.3405 ± .0058 Å respectively for Freon 22. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Standard techniques of radio-frequency nuclear resonance spectroscopy have been applied to further studies of the interaction between atomic nuclei in crystals and the crystalline electric' field gradients at the nuclear sites. Observations have been made on the nuclear magnetic resonance spectra of Al²⁷, Li⁶, Li⁷ and Si²⁹ in single crystals of LiAl(Si0₃)₂ (spodumene) in strong magnetic fields. Results from the Al²⁷ spectrum provided improved values of the field gradient constants of spodumene and a check on the adequacy of second and third order perturbation theory in describing the electrostatic perturbation of the magnetic energy levels; these results also provided an experimental check on a proposed new method of nuclear spin determination. The Li⁶ and Li⁷ measurements provided a more accurate value of the quadrupole moment ratio for this pair of isotopes. Observations on the Si²⁹ spectrum support; existing evidence that the spin of Si²⁹ is 1/2. A super-regenerative spectrometer has been built for the detection of nuclear magnetic resonances and nuclear electric quadrupole resonances. Preliminary tests indicate that it will detect resonances in solids at low frequencies which could not be detected with the continuous-wave type of spectrometer. A pure quadrupole resonance in Na₂B₄O₇.4H₂O (kernite) has been detected at 1.27 Mc./sec. using this super-regenerative spectrometer. This represents a pure quadrupole resonance of the lowest frequency reported to date. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The Lubzinski.spectrograph has been accurately focussed and its performance as a high dispersion vacuum ultraviolet instrument has been studied. Light sources have been designed for the excitation of the hydrogen Lyman series. The α line of this series has been obtained using exposure times ranging from twenty minutes to seven hours. A spectrogram of the hydrogen-deuterium isotope structure obtained in the fifth grating order at a dispersion of 1 A°/mm. has been obtained permitting positive identification of the hydrogen Lyman α line. Light sources for the excitation of the first-spark spectra of copper have, been constructed and experimentally studied. This spectrum contains a large number of standard wavelengths, in the vacuum ultraviolet; however, because of low grating intensity we were unable to observe these lines. An existent discrepancy between calculated and measured, values for the ionization potential of Helium-like atoms has been resolved by a generalized Lamb electromagnetic shift. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The beta and gamma spectra of Fe⁵⁹ have been examined in a thin lens beta ray spectrometer. Gamma rays with energies of 1.10 Mev and 1.29 Mev were detected using the photoelectric technique with a Uranium radiator. Using a thin foil as a source, beta groups with maximum energies of 1.77 Mev and 0.45 Mev were found. There was no evidence of a 0.26 Mev group as reported by other workers. Tentative decay schemes are presented. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No abstract included. / Science, Faculty of / Mathematics, Department of / Graduate

A survey of 21-cm line emission at points equally spaced over the entire sky visible from Penticton, British Columbia, has been made, and the profiles obtained at the intermediate galactic latitudes have been used to determine several of the properties of the distribution of the gas in the solar neighbourhood and to study the dynamics of the gas including the determination of solar motion with respect to gas, the distribution of random velocities and the departure of gas velocities from circular motion. / Science, Faculty of / Physics and Astronomy, Department of / Graduate