Electron Diffraction by the Oxides of Nitrogen

Electron diffraction has been obtained by the transmission of electrons (20-35 kv) through molecular beams of N2O, NO2, N2O4 and N2O5. The molecular structure determinations were made by using the complete electron scattering formula including the incoherent scattering. The results can be summarized as follows: (1) Nitrous oxide; for a linear model the separation of the end atoms was found to be 2.38 +/- 0.05A in exact agreement with Wierl's measurement on this structure. Unfortunately it is impracticable to distinguish between models of the form N-O-N and N-N-O. (2) Nitrogen dioxide; no diffraction rings were observed which is to be expected if the molecule is triangular with the N-O distance 1.15 to 1.3A. (3) Nitrogen tetroxide; the presence of one diffraction ring at (1/lambda) sin theta/2=0.455 +/- 0.01 lead to the conclusion that the N-N distance is 1.6 to 1.7A for the model O2N-NO2. No definite angular relationship between the two planes containing the NO2 groups could be determined. (4) Nitrogen pentoxide; again only one diffraction ring was observed. It occurred at a slightly greater angle than for N2O4 giving (1/lambda) sin theta/2=0.474 +/- 0.004. The symmetrical model O2N-O-NO2 with the N-O distance 1.3 to 1.4A gave a calculated interference pattern in best agreement with this result.