Measurement of the methyl radical concentration profile in a hot-filament reactor
- Department of Chemistry, Stanford University, Stanford, California 94305 (United States)
- Department of Mechanical Engineering, Stanford University, Stanford, California 94305 (United States)
The spatial profile of methyl radical concentration in a hot-filament reactor has been measured using cavity ring-down spectroscopy (CRDS) at a wavelength of 213.9 nm for which the CH{sub 3} absorption cross section has been shown to be nearly independent of temperature. Methyl radicals are generated with a 25 mm long tungsten filament heated to 2400 K in a slowly flowing mixture of 0.6% CH{sub 4} in H{sub 2} (20 Torr total pressure). CRDS is employed to measure CH{sub 3} absorbance as a function of a distance perpendicular to the axis of the filament. The CH{sub 3} absorbance profiles do not change when the direction of the process gas flow through the reactor is reversed, which indicates cylindrical symmetry of the CH{sub 3} distribution about the filament. Consequently, the radial CH{sub 3} concentration in the reactor is determined by Abel inversion of the CH{sub 3} absorbance profile. The CH{sub 3} concentration peaks {similar_to}4 mm from the filament (1.04{times}10{sup 14} molecules/cm{sup 3}). Methyl radicals decay rapidly as a function of a distance from the filament and disappear about 2 cm from the filament within our present detection sensitivity (3{times}10{sup 12} molecules/cm{sup 3}). {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
- DOE Contract Number:
- FG03-92ER14304; FG03-88ER13957
- OSTI ID:
- 69037
- Journal Information:
- Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 1 Vol. 67; ISSN APPLAB; ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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