The internal energy distribution of atom-recombination product N2 desorbing from polycrystalline Fe

The vibrational and rotational energies of recombination product nitrogen molecules desorbing from a polycrystalline iron surface were measured. The internal energy of the product gas was determined by electron beam induced fluoresence and surface composition was monitored by soft x-ray appearance potential spectroscopy. For clean iron with surface temperature ranging from 1086 to 1390 K, the vibrational temperature remained relatively constant, within the error limits, at a temperature slightly above that of the surface. Vibrational temperatures significantly higher than the surface temperature were found for sulfur contaminated surfaces. A rotational temperature of 400±30 K was observed for both the clean and sulfur covered surfaces between 1086 and 1239 K. A model incorporating surface imposed steric constraints causing the low rotational energies and potential barriers to reaction affecting vibrational energies is proposed.