Coherent nanodiffraction from phase objects: carbon nanotubes

Electron diffraction patterns obtained with a coherent incident beam of diameter 1 nm or less do not, in general, show a center of symmetry even for thin phase objects. Experimental observations of nanodiffraction patterns obtained from the walls of carbon nanotubes show asymmetries in the intensities of the first-order reflections from the carbon-layer stacking periodicity which are in agreement with calculations from a simple theoretical model. It is suggested that the measurement of such asymmetries may provide evidence regarding the structures of nanotubes of non-circular cross-section and of the end regions of tubes.