Molecular Structure Determination by Gas Electron Diffraction at High Temperatures. I. Arsenic

Abstract
A high-temperature nozzle assembly for gas-electron diffraction has been designed and constructed. The molecular structure of gaseous arsenic at 485°C has then been investigated by the use of this nozzle. The regular tetrahedral structure of the molecule has been confirmed from the observed index of resolution; the interatomic distance has been determined to be rg(As−As)=2.435±0.004Å, while the mean amplitude has been determined for the first time (l(As−As)=0.085±0.006Å). The observed amplitude has led to the evaluation of the bond-stretching force constant, fr(As−As)=1.5±0.3 mdyn./Å.