Two-dimensional laser induced fluorescence measurements are applied to the chemical vapor deposition of diamond by an oxyacetylene flame. The fluorescence distributions of C2, CH, and OH are measured for various deposition conditions. The influence of the temperature of the molybdenum substrate and the distance between the substrate and the flame front on the two-dimensional distributions and on the quality and morphology of the deposited diamond is investigated. A relation is observed between the C2 distribution in the flame and the local growth rate and quality of the diamond layer, therefore C2 is thought to be an important species for diamond growth. The exact role of CH as a growth species is less clear; OH seems to be of minor importance. All measurements are performed during diamond deposition. 0 1995 American Institute of Physics.

Parity resolved state-to-state cross sections for rotational excitation ofOH(X 2n) colliding with He and Ar, have been obtained in a crossed molecular beam experiment. The OH radicals were produced in a pulsed dc discharge in a H 2 0/ Ar gas mixture. Adiabatic expansion into vacuum resulted in an effective rotational cooling yielding a 94% population of the lowest A-doublet (X 2n3/2' J=~). Further state preparation could be achieved via electrostatic state selection in a hexapole electric field, resulting in a 93.5% population of the upper A-doublet component (f, + ). Experiments were performed both with and without the state selector to provide detailed information about the rotational excitation from both A-doublet states. The OH rotational state distribution was probed, before and after the collision event, by means of laser-induced fluorescence (LIF) spectroscopy of the A -X electronic band at 308 nm. The OH-Ar and OH-He scattering behave very similar with the exception of the J=~ A-doublet transition which is induced much weaker by the He collisions.

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