Abstract
The molecular structure of perylene has been studied in the vapour phase by the sector electron diffraction method. The average carbon-carbon bond distance in perylene apart from the peri-bonds was found to be about 0.010 $\overset{\circ}{\mathrm A}$ longer than the average carbon-carbon bond distance in the naphthalene molecule. The peri-bond length was determined to be 1.493 $\pm$ 0.015 $\overset{\circ}{\mathrm A}$.