Spectroscopic characterization of Stone-Wales defects in nanotubes

We combined resonant photoabsorption and vibration spectroscopy with scanning tunneling microscopy (STM) to unambiguously identify the presence of Stone-Wales (SW) defects in carbon and boron nitride nanotubes. Based on extensive time-dependent ab initio density functional calculations, we propose to resonantly photoexcite SW defects in the infrared and ultraviolet regime as a means of their identification. Onset of nonradiative decay to a local defect vibration with a frequency of 1962cm^-1 serves as a fingerprint of such defects in carbon nanotubes. The bias dependence of the STM images shows distinct features associated with the presence of SW defects.