Laser-induced fluorescence in the CH (<i>B</i> – <i>X</i>) and CH (<i>A</i> – <i>X</i>) electronic transitions is used to measure absolute number density versus position for CH radicals in the plume of a 25-Torr hydrogen/argon/methane (0.8:1:0.005) dc arcjet during the chemical vapor deposition of diamond film. The laser-induced-fluorescence signal is calibrated with argon Rayleigh scattering, and the resultant concentration of the CH radical in the center of the arcjet plume is found to be (3.5 ± 0.8) × 10<sup>12</sup> molecules/cm<sup>3</sup>. The characterization of the plasma plume shows three different regions in the reacting gas: nozzle, plume, and boundary layer. We observe substantial differences in spatial distribution of gas temperature, collisional quenching, and CH number density among these regions.
© 1997 Optical Society of America
J. Luque, W. Juchmann, and J. B. Jeffries, "Absolute concentration measurements of CH radicals in a diamond-depositing dc-arcjet reactor," Appl. Opt. 36, 3261-3270 (1997)