The reactive scattering of O2, from a pulsed molecular beam, with a hot Si(100) (about 1250 K) has been studied with resonance enhanced multiphoton ionization (REMPI) mass spectroscopy in the wavelength region between 282 and 295 nm (F 1Σ+←X 1Σ+ and H 1Σ+←X 1Σ+). The vibrational and rotational state distributions of scattered SiO species are Boltzmann with temperature near that of the Si(100) surface. An isotropic angular distribution of the SiO desorption is observed and the internal state distribution is independent of the desorbing angle. The results suggest that the SiO desorption goes through a state in which the SiO rotates almost freely.