Synchrotron radiation photoelectron spectra

Accurate investigation of the valence ionization spectra is important subject to elucidate the electronic structure of molecules. Ionization spectra of five-membered aromatic compounds have also been intensively studied. The high-resolution synchrotron radiation photoelectron spectra (SRPES) of furan and thiophene were measured and analyzed with asymmetry parameter up to about 40 eV [63,64]. The electron momentum spectroscopy (EMS) was also applied to furan up to 30-40 eV [65]. The ionization spectra of these molecules were also studied by several theoretical methods. However, there were some controversial assignments even for the outer-valence region, in particular for the peak position of Ibi(TTi) state and the inner-valence spectra have not been theoretically reproduced. 

Figure 2 Molybdenum K-edge X-ray absorption spectrum, ln(i /i ) versus X-ray energy (eV), for molybdenum metal foil (25- jjn thick), obtained by transmission at 77 K with synchrotron radiation. The energy-dependent constructive and destructive interference of outgoing and backscattered photoelectrons at molybdenum produces the EXAFS peaks and valleys, respectively. The preedge and edge structures marked here are known together as X-ray absorption near edge structure, XANES and EXAFS are provided in a new compilation of literature entitled X-rsy Absorption Fine Structure (S.S. Hasain, ed.) Ellis Norwood, New York, 1991.

Fig. 11.2. The total photoelectron yield spectrum of lanthanum in the solid phase, as obtained by synchrotron radiation spectroscopy in the neighbourhood of the 3d threshold. Curve (a) shows the experimental data points with the sum of two Lorentzian profiles fitted to them. Curve (b) shows the same data points for the higher of the two resonances, with a Fano profile fitted to it. The improvement in the fit is clear evidence for a slight asymmetry due to autoionisation (after R.C. Karnatak et al. [599]).

The photoelectron spectra can be generated using a primary beam of ultraviolet radiation (known as ultraviolet photoelectron spectroscopy (UPS)), or X-rays to yield an XPS spectrum. It can also be generated by synchrotron radiation (SR), in which case the electron spectrometer must be attached to the beam line at a synchrotron facility. UPS is essentially a molecular spectroscopy that provides high-resolution valence band spectra, while XPS is used predominantly to study core level transitions, and also to study valence band electrons. 

Electron densities n (in 10 cm ) of 1.53,2.05, and 2.3 have been derived from spectroscopic studies on Tm Se with x = 0.87, 1.0, and 1.05 at room temperature. These were compared with 1.5,2.05, and 2.3, calculated assuming one electron per Tm. The effective optical mass for all these samples is m = 1.65 mo- The effective number of electrons per formula unit for TmSe at 2.5 eV is neff = 0.86. A figure in the paper for the range -0 to-6.5 eV shows an increase from -0 at -0 eV to neff 2.5 at 6.5 eV, Batlogg [18], see also [19]. Electron mean free paths of 8.0 and 6.2 A are derived for nearly stoichiometric TmSe from the photoelectron spectrum induced by synchrotron radiation (UPS), Kaindl etal. [20, 21]. 

Other techniques utilize various types of radiation for the investigation of polymer surfaces (Fig. 2). X-ray photoelectron spectroscopy (XPS) has been known in surface analysis for approximately 23 years and is widely applied for the analysis of the chemical composition of polymer surfaces. It is more commonly referred to as electron spectroscopy for chemical analysis (ESCA) [22]. It is a very widespread technique for surface analysis since a wide range of information can be obtained. The surface is exposed to monochromatic X-rays from e.g. a rotating anode generator or a synchrotron source and the energy spectrum of electrons emitted... 

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