title: Absolute concentration measurements of CH radicals in a diamond-depositing dc-arcjet reactor.
abstract: Laser-induced fluorescence in the CH (B - X) and CH (A - X) 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) x 10(12) molecules/cm(3). 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.
authors.forename: J
authors.initials: J
authors.lastname: Luque
authors.forename: W
authors.initials: W
authors.lastname: Juchmann
authors.forename: J B
authors.initials: JB
authors.lastname: Jeffries