A high power pulsed CO_2 laser was used to induce reactions in gas mixtures containing either N_2F_4 or SF_6. The rate of laser induced dissociation of N_2F_4 to NF_2 was as much as 1000 times faster than the thermal rate, and the rate law was of lower order than the thermal, bimolecular rate law. Explosion threshold and induction time data were obtained for butene stabilized mixtures of N_2F_4 and H_2. HF laser gain was observed during the first few microseconds of CO_2 laser pulse, but it was strongly quenched by the explosion. The laser driven reaction of SF_6 with H_2 also exhibited HF laser gain at early times and laser energy threshold for reaction. All of the laser induced reactions studied occurred at rates that were faster than the rates of thermal reaction. This accelerated reaction rate was attributed to nonthermal vibrational excitation of the reactants. A computer model of the SF_6-H_2 electrical discharge chemical laser was employed to gain a better understanding of the fundamental processes that occur in this laser. Good agreement with experimental results were obtained, and several suggestions for further study were made.

<p> Acceptor compounds of C60 and hexafluoride ions of group V elements (P, As, Sb) were studied by infrared spectroscopy, x-ray diffraction and resistivity measurements. C60(AsF 6)1.9 was formed by reacting C60 powder with AsF5 gas dissolved in liquid S02. The AsF 6 ion was identified by a broad v3 absorption at 703 cm^-1, a shoulder at 681 cm^-1 and evidence of the sharp v4 absorption just below 400 cm^-1 in the infrared spectrum. The low frequency modes ofC60 at 527 and 576 cm^-1 were unshifted in the reacted powder. The T1u(3) mode of C60 , at 1183 cm^-1 was accompanied by neighbouring absorptions at 1194 and 1206 cm^-1, which were assigned tentatively to splitting of the triply degenerate mode. Three strong peaks at 1549, 1406 and 1322 cm^-1 observed in the spectra were assigned to splitting of the threefold degenerate T1u(4) mode of pristine C60 at 1428 cm^-1. Heat treatments ofthe sample, with temperatures ranging up to 350°C, were performed to thermally deintercalate the sample and to aid in identifying the infrared modes. The decrease in intensity ofthe AsF6 absorptions and the return ofthe four strong absorption lines ofundoped C60 indicated the successful deintercalation of the sample. X-ray diffraction indicated that the C60 lattice, which had expanded to body centered tetragonal to accommodate the AsF 6 ion, returned to the face centered cubic arrangement of pristine C60 following heat treatments at 350 degrees Celcuis. The C60(AsF6)1.9 compound exhibited semiconductor characteristics with an activation energy of 0.12 ± 0.05 eV. Possible interstitial sites for the AsF6- ion in the body-centered-tetragonal lattice of C60(AsF 6)1.9 have also been calculated. </p> <p> The PF6 ion, in the sample of C60 reacted with N02PF6 in S02, was observed in the IR spectra by the broad v3 absorption at 830 cm^-1 and the sharp v4 absorption at 558 cm^-1 No strong absorption of NO2+ at 2360 cm^-1 was observed indicating that the sample was not a simple mixture of the two powders. The C60 absorption lines, at 527, 576, I I 83 and 1428 cm^-1 were unshifted. However, the T1u(4) mode at 1428 cm^-1 showed asymmetric broadening on the low frequency side and small absorptions flanking the T 10( 4) mode. These features, although much less pronounced, may correspond to the shifting and splitting observed in the T1u(4) mode ofthe C6o{AsF6)1.9 compound. The octahedral SbF6- ion was identified in the sample of C60 powder reacted with N02SbF6 by the strong v3 absorption at 660 cm^-1. The C60 lines were unshifted, but small absorptions flanking the T1u(4) mode, are again similar to the absorptions assigned to splitting in the C60(AsF6)1.9 compound. </p> / Thesis / Master of Science (MSc)

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