[en] A high pressure, radio frequency discharge nozzle beam source was developed for the production of very intense (greater than or equal to 10¹⁸ atoms sr^-1 sec^-1) supersonic beams of oxygen atoms. This source is capable of producing seeded beams of ground state O(³P/sub J/) atoms when dilute oxygen-argon mixtures are used, with molecular dissociation levels exceeding 80% being realized for operation at pressures up to 350 torr. When dilute oxygen-helium mixtures are employed both ground state O(³P/sub J/) and excited state O(¹D₂) atoms are present in the terminal beam, with molecular dissociation levels typically exceeding 60% being achieved for operation at pressures up to 200 torr. Atomic oxygen mean translational energies from 0.14 to 0.50 eV were obtained using the seeded beams technique, with Mach numbers as high as 10 (FWHM Δ v/v approx. = 20%) being realized. The IC1, CF₃I, C₆H₆, and C₆D₆ reactions are discussed in detail. The IC1 and CF₃I studies have enabled us to determine an improved value for the bond energy of the IO radical: D/sub o/(IO) = 55 +- 2 kcal/mole. The IO product angular and velocity distributions have been used to generate center-of-mass flux contour maps, which indicate that these two reactions proceed via relatively long-lived collision complexes whose mean lifetimes are slightly shorter than their respective rotational periods. The O(³P/sub J/) + C₆H₆ and C₆D₆ reactions were studied in order to elucidate the reaction mechanism, and, in particular, to identify the primary reaction products produced in these reactions. Finally, a series of beam-surface scattering experiments are described which examined the internal and translational energy dependence of molecular condensation probabilities for collisions involving either CC1₄ or SF₆ and their respective condensed phases. 117 references