The hyperthermal beams were directed at a FiberForm sample with an incidence angle of θi = 45°, and the products that scattered from the sample were detected by the rotatable mass spectrometer detector at various scattering (or final) angles, θf. Although the sample was a threedimensional network of carbon fibers, the dimensions of the fibers and the spaces between them were far smaller than the overall sample dimensions, allowing a nominal surface to be defined.