Measuring the true helicity of carbon nanotubes

Electron diffraction patterns from carbon nanotubes have been analyzed for measuring the true helicity of carbon nanotubes. The cylindrical curvature of the tubules causes a large difference between the apparent half twist angle which appears in electron diffraction patterns and the true helical angle of the examined tubule. A direct method has been developed to calculate the cylindrical correction factors, which are vital for accurate deduction of the true helicity from electron diffraction patterns. By combining with measured diameters from real-space images, it is now possible to determine the atomic structure of carbon nanotubes.