Photoionization cross section of image potential states around nanotubes

Abstract

In this paper, we theoretically address the photoemission from image potential states (IPS) around nanotubes. The relevance of this process is related to the fact that this particular kind of IPS has been experimentally detected for carbon nanotubes by means of femtosecond-resolved two-photon photoemission (Zamkov et al 2004 Phys. Rev. Lett. 93 156803). The quantum interaction between the bound electron and the incident radiation field is considered within the dipolar approximation, and the transition matrix for the process is obtained using a first-order Born expansion. For a linearly polarized photon with the polarization vector perpendicular to the nanotube's axis, electrons are found to be emitted with a polar angle that is determined by the initial parallel momentum of the bound electron.