Inverse photoemission experiments

The main evidences collected about the metallization of the AM-Si(100)2xl have been obtained from direct and inverse photoemission experiments. Early results [87Ent, 89Ent, 89Kon] showed that the K/Si(100)2xl and Cs-covered surfaces have a band gap, with no density of states at the Fermi energy for... 

There is much consensus between the cluster and periodic modeling results compared to experiment, especially in regards to the band structure and 0 K magnetism. Deductions regarding the electronic structure from photoemission and inverse photoemission experiments indicate that the upper valence band consists of a wide, bonding O 2p-Fe 3d band, and the conduction band is a more narrow antibonding O 2p... 

A similar two-peak structure is seen in the inverse photoemission (bremsstrahlung isochromat spectroscopy (BIS)) spectra of cerium (Land et al. 1981) and several of its compounds (Allen et al. 1983). (In a BIS experiment, one adds an electron to the system.) The first peak is just above p ( 0.5eV) and is dominant in the more itinerant cerium compounds. The second peak is located 4-5eV above the pand is due to localized f -> P transitions. The BIS spectrum in certain ways thus mirrors what is seen in the photoemission spectrum. With this in mind, it was decided to apply the techniques of the preceding sections to determine the inverse photoemission spectrum of CeP (Norman, 1985). 

The complementary method to time-resolved measurements is the spectroscopy in the energy domain. Energy-resolved experiments determine the Fourier transform of the exponential decay in the time domain, which yields a Lorentzian for the intrinsic spectral lineshape. As mentioned in Section 3.2.4, photoemission does not permit to separate inelastic and elastic decay processes, which both contribute to the linewidth. Because the energy resolution of inverse photoemission is usually not sufficient for a lineshape analysis, this section is devoted to photoemission of occupied states, providing an additional complementary aspect to the time-resolved measurements of transiently populated unoccupied states by 2-PPF. Occupied (initial) states can also be observed by 2-PPE spectroscopy. Their linewidth is similar to the values obtained in regular photoemission [107]. 

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