The Hydrogen Induced State on Gd

Additionally, information on quantum mechanical quantities are usually obtained with a more or less larger experimental or theoretical effort. Being in contrast, the theoretical description of the latter type of angle resolving photoemission experiments as well as the experimental procedure are relatively simple. This method is suitable to be carried out in a laboratory because it does not need a sophisticated experimental setup as synchrotron radiation sources. It may therefore play an important role for a proceeding understanding of the photoemission process. 

In the following it will be reported on a straightforward method to provide information about the dipole matrix elements and phase shifts being essential for the theoretical description of the photoemission process in a relatively simple way and with a pronounced accuracy [2]. This can be achieved by means of photoelectron spectroscopy with linearly polarized light using the ability of a continuous rotation of the electric field vector. The method is exemplarily demonstrated at the system hydrogen on Gd(0001)/W(l 10) which possesses a pronounced adsorbate induced state. 

Photoelectrons were produced using linearly polarized vacuum ultraviolet (VUV) radiation from a discharge lamp (Ne i resonance line hv = 16.85 eV) with a triple reflection polarizer. The angle of the incoming photon beam was 0ph = 45° with respect to the surface normal. The experimental setup is schematically shown in Fig. 4.1. 

Photoelectron spectra from the clean Gd(OOOl) surface and after hydrogen exposures are presented in Fig. 4.2. The spectra were taken in normal emission at room temperature. The sharp feature near the Fermi edge is due to the Gd surface 

The E vectOT of the incoming linearly polarized radiation can be rotated as indicated by the circle 

---