The Nuclear Separation of theS2Molecule by Electron Diffraction

Rotational analyses of ${\mathrm{S}}_{2}$ bands as carried out by various workers have led to the following values for the nuclear separation; 1.60A, 1.84A, 1.73A, and 1.93A. In the present work this distance was determined by electron diffraction from ${\mathrm{S}}_{2}$ vapor at 800\ifmmode^\circ\else\textdegree\fi{}C and was found to be 1.92\ifmmode\pm\else\textpm\fi{}0.03A. This value is based upon the measured relative intensities of scattering in the region of the third maximum, $(\frac{1}{\ensuremath{\lambda}})sin\frac{1}{2}\ensuremath{\theta}$ from 0.70 to 1.0, and upon visual measurements on the fourth, fifth and sixth diffraction maxima. When the temperature of sulphur vapor is decreased appreciably below 800\ifmmode^\circ\else\textdegree\fi{}C its electron diffraction pattern shows the presence of higher molecular types. The results obtained can be explained on the basis of ${\mathrm{S}}_{2+n}$ molecules where $n=1,2,3\ensuremath{\cdots}$ with a S---S---S valence angle of about 100\ifmmode^\circ\else\textdegree\fi{} and a S---S distance, between closest neighbors, of ca. 2.1A. These values are in agreement with those found for the symmetrical puckered ring-shaped ${\mathrm{S}}_{8}$ molecule present in crystalline sulphur.