Electron-stimulated ion

Xeels = electron energy loss spectroscopy. y hreels = high resolution electron energy loss spectroscopy. Z ceels = core level electron energy loss spectroscopy. aaesdiad = electron-stimulated ion angular distribution. 

ESI-FTMS Electrospray ionization Fourier transform mass spectrometry ESID Electron stimulated ion desorption... 

ESD Electron-stimulated (impact) desorption [148, 149] An electron beam (100-200) eV) ejects ions from a surface Surface sites and adsorbed species... 

ESDIAD Electron-stimulated desorption ion angular distribution [150-152] A LEED-like pattern of ejected ions is observed Orientation of adsorbed species... 

The nature of reaction products and also the orientation of adsorbed species can be studied by atomic beam methods such as electron-stimulated desorption (ESD) [49,30], photon-stimulated desoiption (PDS) [51], and ESD ion angular distribution ESDIAD [51-54]. (Note Fig. VIII-13). There are molecular beam scattering experiments such... 

An electron or photon incident on a surface can induce an electroiuc excitation. When the electroiuc excitation decays, an ion or neutral particle can be emitted from the surface as a result of the excitation. Such processes are known as desorption induced by electroiuc transitions (DIET) [82]. The specific teclmiques are known as electron-stimulated desorption (ESD) and photon-stimulated desorption (PSD), depending on the method of excitation. 

A number of surface-sensitive spectroscopies rely only in part on photons. On the one hand, there are teclmiques where the sample is excited by electromagnetic radiation but where other particles ejected from the sample are used for the characterization of the surface (photons in electrons, ions or neutral atoms or moieties out). These include photoelectron spectroscopies (both x-ray- and UV-based) [89, 9Q and 91], photon stimulated desorption [92], and others. At the other end, a number of methods are based on a particles-in/photons-out set-up. These include inverse photoemission and ion- and electron-stimulated fluorescence [93, M]- All tirese teclmiques are discussed elsewhere in tliis encyclopaedia. 

Other techniques in which incident photons excite the surface to produce detected electrons are also Hsted in Table 1. X-ray photoelectron Spectroscopy (xps), which is also known as electron spectroscopy for chemical analysis (esca), is based on the use of x-rays which stimulate atomic core level electron ejection for elemental composition information. Ultraviolet photoelectron spectroscopy (ups) is similar but uses ultraviolet photons instead of x-rays to probe atomic valence level electrons. Photons are used to stimulate desorption of ions in photon stimulated ion angular distribution (psd). Inverse photoemission (ip) occurs when electrons incident on a surface result in photon emission which is then detected. 

ESDIAD Electron-stimulated desorption ion angular distribution IPES Inverse photoemission spectroscopy... 

Electron Stimulated Desorption (ESD) and ESD Ion Angular Distribution (ESDIAD)... 

The most common ions observed as a result of electron-stimulated desorption are atomic (e. g., H, 0, E ), but molecular ions such as OH", CO", H20, and 02" can also be found in significant quantities after adsorption of H2O, CO, CO2, etc. Substrate metallic ions have never been observed, which means that ESD is not applicable to surface compositional analysis of solid materials. The most important application of ESD in the angularly resolved form ESDIAD is in determining the structure and mode of adsorption of adsorbed species. This is because the ejection of positive ions in ESD is not isotropic. Instead the ions are desorbed along specific directions only, characterized by the orientation of the molecular bonds that are broken by electron excitation. 

Electron spin resonance (esr), 22 132 for lignin characterization, 15 10 Electron-stimulated desorption-ion angular distribution (ESDIAD), 24 74 Electron transfer (ET), 9 376-381, 388 mechanisms of, 13 444 rate constant for, 13 447 Electron-transfer dynamics, in... 

Anion Desorption Measurements. Reactive scattering by DEA fragment ions in condensed media was first noted in the form of OH electron-stimulated desorption (ESD) yields from O2 embedded in multilayer alkane films [246] and subsequently for aniline physisorbed on top of O2 solids [215]. The anion produced following DEA to N2O has also been observed to react with other N2O molecules within an Ar/N20 matrix to generate a desorbed yield of NO and NO2, among other products. Part of the H2 ESD yield observed from multilayer films of H2O, at incident electron energies below 10 eV, has also been attributed to proton abstraction by fragments produced by DEA, viz., -I- H20 H30 ... 

Many of the mechanisms discussed in Sect. 2.2.6.1 with regard to ions may also apply to chemical reactions enhanced by electron bombardment. A discussion of that type will not be repeated in this section. However, a mechanism for the electron-enhanced etching of SiOj can be suggested on the basis of processes which are known to occur. It is known, for example, that electron bombardment of SiOj causes oxygen to be desorbed into the gas phase, i.e., electron stimulated desorption occurs . The silicon which remains upon the surface can now be attacked by the XeFjfgas) to produce SiF4(gas). In this manner both oxygen and silicon are removed from the SiOj lattice and the material is etched. The chemistry involved is likely to be more complex, but this simple model illustrates a possible mechanism. 

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