Angle-resolved photoelectron spectra

Figure 4 Angle-resolved photoelectron spectra for Ni 100] ( 2x/2)R45°-CO. hv = 32 eV (a) angle of incidence, o = 60°, polar angle of emission, 0 = 0°. (b) a = 0 , 0 = 50°, Elk). Inset Gas phase photoelectron spectrum of CO at the same photon energy. After [10] and [11].

Figure 10 Angle-resolved photoelectron spectra from the system Cu 11D -HC00 for three different emission angles, hv = 25°, E j <110>. After [251.

Molecular alignment (see Section 8.11.2) can be probed by measurement of the circular dichroism in the photoelectron angular distribution (CDAD). CDAD spectra are obtained by taking the difference between angle-resolved photoelectron spectra for left and right circularly polarized light (Dubs, et al., 1986). 

For a discussion of the calculation of time and angle resolved photoelectron spectra, we refer to the recent papers of Seideman and... 

In this section we have discussed the requisite extension of our theory of energy- and angle-resolved photoelectron spectra for pump-probe ionization... 

Figure 10.14 Angle-resolved photoelectron spectra of the clean C(lll)2xl surface scanning the surface Brillouin zone along a line through K. The resonance S corresponds to the surface state, K is reached for a polar angle of ft 45. The zero of the energy axis is the Fermi level. In the upper panel one spectrum for the hydrogen-terminated surface is shown to demonstrate the absence of S for that surface. (Data from Ref [57].)...

In the investigations of molecular adsorption reported here our philosophy has been to first determine the orientation of the adsorbed molecule or molecular fragment using NEXAFS and/or photoelectron diffraction. Using photoemission selection rules we then assign the observed spectral features in the photoelectron spectrum. On the basis of Koopmans theorem a comparison with a quantum chemical cluster calculation is then possible, should this be available. All three types of measurement can be performed with the same angle-resolving photoelectron spectrometer, but on different monochromators. In the next Section we briefly discuss the techniques. The third Section is devoted to three examples of the combined application of NEXAFS and photoemission, whereby the first - C0/Ni(100) - is chosen mainly for didactic reasons. The results for the systems CN/Pd(111) and HCOO/Cu(110) show, however, the power of this approach in situations where no a priori predictions of structure are possible. 

These conclusions were supported by results obtained from angle-resolved XPS. The band near 932.4 eV in the Cu(2pV2) photoelectron spectrum of the mirror coated with y-APS increased in intensity relative to that near 934.9 eV when the take-off angle was increased from 15° to 75°. Similarly, the band near 336.8 eV in the Auger spectrum also increased in intensity relative to that near 340.0 eV. Such behavior would be expected if the bands near 932.4 eV in the photoelectron spectrum and near 336.8 eV in the Auger spectrum were related to an oxide that was covered by a thin film of silane. 

Results. It was found that XPS spectra of mixed oxides could be interpreted using only the U + and U + oxidation states. A 1.3 + 0.2 eV shift existed between these two states which was maintained for mixed valence oxides. The U(4f ) photoelectron spectra for UO2 is shown in Fig. 4a while the spectra for a surface oxidized at - -300 mV is shown in Fig. 4b. The peak fits obtained, maintaining the 1.3 eV separation between UO2 (+4) and U03(-)-6), show good fits to the data and were used to determine the ratio of U +/U + in the surface oxide. Angle resolved XPS measurements indicated that the surface oxide was sufficiently thick after two minutes of oxidation to prevent any U +(U02) contribution to the spectrum from the UO2 substrate. 

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