Observation of surface-induced photon fields in the photoemission of 1T-TiS2

Normal-emission spectra from 1T-${\mathrm{TiS}}_2$ have been calculated within the one-step model with explicit consideration of the dielectric response to the incident p-polarized photon field, because calculations within the dipole approximation failed to explain relative intensities of experimental energy distribution curves. Following the hydrodynamic model we added to the photon vector potential a longitudinal plasmon-induced plane wave. We show that these corrections generally are of distinct importance, and, in the present case, lead to an essentially better agreement between theoretical and experimental spectra.