Reactive and inelastic scattering dynamics of hyperthermal O and O₂ from a carbon fiber network

Pulsed beams containing O and O₂ with incident velocities of ∼7900 m s⁻¹ were directed at a carbon fiber preform network (FiberForm) at temperatures in the range, 1023–1823 K, and the products that scattered from the network were detected with a rotatable mass spectrometer as a function of their velocities and scattering angles. A beam containing pure Ar atoms was also directed at the network, allowing multiple-bounce effects in the absence of reaction to be characterized. Scattered O, O₂, and Ar exhibited the dynamical characteristics of impulsive (non-thermal) scattering and thermal desorption (TD). On the other hand, CO and CO₂ exhibited only TD dynamics. The fluxes of all products were quantified as a function of sample temperature and, for two focus temperatures, as a function of scattering angle. CO was the dominant reactive product. A temperature dependent hysteresis in the CO flux was quantified, and a comparison was made between the hysteresis on the carbon fiber network and on a planar vitreous carbon surface. The new results may be used to increase the fidelity of oxygen-carbon ablation models for hypersonic flight.