Total electron yield

Figure 6 Total electron yield as a function of the primary electron s energy when it arrives at the surface of the specimen.

Soft X-ray absorption measurements are done at low-energy synchrotron X-ray facilities such as the UV ring at NSLS or the Advanced Photon Source (APS) at Lawrence Berkeley National Laboratory (LBNL). The beam size is typically 1 mm in diameter. The electron yield data are usually obtained in the total electron yield (EY) mode, measuring the current from a channel electron multiplier (Channeltron). Sometimes a voltage bias is applied to increase surface sensitivity. This is referred to as the partial electron yield (PEY) mode. Huorescence yield (EY) data are recorded using a windowless energy dispersive Si (Li) detector. The experiments are conducted in vacuum at a pressure of 2 X 10 torr. 

Fig. 25 Normalized total electron yield Fe E23-edge XANES spectra for FeAsi-yPy. The small shoulders just above the L3 and L2 edges in FeAs0.10P0.90 probably arise from some surface oxide formed. Reprinted with permission from [61], Copy- w,...

Fig. 1, Total electron yield (TEY) SEXAFS raw data on the K edge of Co overlayers on Si(lll) 7x7 surfaces, and of CoSij. The bottom curve is for 2 mono-layers of Co on Si(lll) as deposited at room temperature. The reaction of Co with the Si substrate is seen from the similarity of the EXAFS oscillations with those of the CoSij standard (top curve). The central spectrum was obtained from 30 ML Co/Si(lll) as deposited at room temperature, and it is dominated by the EXAFS of unreacted Co. (Rossi et al. unpublished results)...

Fig. 6. Total electron yield versus ion kinetic energy for singly charged ions of the noble gases incident on atomically clean tungsten. Ions are all in the ground state. (From Ref. )...

Figure 17.2. Carbon NEXAFS spectrum of NOM from the Suwannee River (IHSS standard humic acid mounted on indium foil total electron yield using a dwell time of 200 msec and an exit slit of 50 xm, calibrated to CO at 287.38 eV, Canadian Light Source SGM beamline 11-ID.l) to show pre-edge features and the so-called edge . The spectrum is deconvoluted using a series of Gaussian curves (G) at energy positions of known transitions, along with a step function at the edge as described by Solomon et al. (2005). See color insert.

In concentrated systems obtained in a thin uniform shape, the simplest way to record X-ray absorption data is the transmission mode in which the incident and transmitted photons are directly measured by means of ionisation chambers. However, in dilute systems or for surface characterisations, data are usually recorded using secondary effects resulting from the creation of the core hole during the absorption process and from its subsequent relaxation by radiative or non-radiative decays. These processes are the X-ray fluorescence emission and the total electron yield (TEY) emission, respectively. In these detection modes, the linear absorption coefficient is proportional to the ratio of the fluorescence or TEY intensity to... 

XANES spectroscopy has been used to study the composition and mechanism of antiwear tribofilm formation. The absorption XANES spectra were recorded in total electron yield (TEY) versus fluorescence yield (FY) detection to investigate the chemical nature of P, S, Ca, O and Fe on the surface and in the bulk, respectively. The application of XANES surface TEY mode which analyzes the top 5 nm layer, and the FY technique which analyzes the 50 nm layer of the bulk, taken together, give a marvelous opportunity to study nondestructively the antiwear tribofilms. Both techniques can be used under a wide variety of conditions e.g., the formation of tribofilms at different rubbing times, load, concentrations, temperatures and surface roughness (Kasrai et al., 1993 and 1996 Koningsberger and Prins, 1988 Martin et al., 2001 Yin et al., 1997a). 

FIGURE 14. Normal (denoted by N) and resonant Auger spectra of LiF. Inset shows the total electron yield spectrum of LiF at the F K edge. Labels a-e indicate the mean photon energies where the electron spectra were recorded. The normal Auger electron spectrum was taken at hv = 800 eV. (by Aksela et al. in Phys. Rev. B49 (1994-1) pp, 3117 [26])... 

K at increasing exposures (0.1L-80L) on crystalline ice films obtained by water deposition on a Pt(l 11) substrate held at 150 K. The NEXAFS measurements were performed in the total electron yield (TEY) mode using the monochromatic soft X-ray radiation of SA22 beam line of Super ACO at the LURE facility (Orsay, France). The resolution was 0.02 eV at 190 eV. The PSD NEXAFS have been measured in the total ion yield mode, using a two stages microchannel plates detector. The experimental conditions are detailed in ref 4. 

One of the sure signs of quasiatomic behaviour is the persistence of multiplet structure in the spectrum of the solid. A very good example occurs in the 3d —> f spectra of La the triplet excited states are bound states localised in the inner well of a double-valley potential, while the singlet excited state is resonantly localised in the inner well of the slightly shallower singlet potential. All these states survive in the solid, and one thus observes the full 3Di, 3 Pi and lP multiplet structure very clearly in total electron yield spectra obtained from the surface of the solid (see fig. 11.2). There is even evidence of asymmetry in one of the resonances, which shows that continuum effects other than Auger broadening of the core states are involved, as one expects for atoms. 

For bulk measurements the total electron yield, which has been found to be pro-... 

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