VUV polarimeter for inverse photoemission

In angle-resolved photoelectron spectroscopy (ARPES) experiments, the use of polarized light for excitation provides access to the orbital symmetries of the electronic states under investigation. In angle-resolved inverse photoemission (IPE), the equivalent approach is the polarization analysis of the emitted light. So far, this light-polarization analysis has been neglected for intensity reasons due to the much lower cross section of the transitions in IPE compared with ARPES and the lack of suitable polarizers in the vacuum ultraviolet (VUV) spectral range. In this paper, we present the first VUV polarimeter for IPE. A mirror with a polarizing coating of high reflectivity in Brewster-angle geometry is used. An easy-to-use attachment to established photon detectors with high reflectivity and polarization power is presented and tested. We performed IPE measurements of the well-studied L-gap surface state of Cu(111) with separate detection of p- and s-polarized light. The data show strongly enhanced photon intensity for p polarization compared with the intensity for s polarization. Our results are in accordance with the polarization-dependent ARPES measurements of the occupied part of the surface state.