Electron-induced dissociation

As an example, XPS has been used to analyze modifications induced by 2 to 20 eV electrons incident on a hydrogen-passivated and sputtered Si(lll) surface, onto which had been physisorbed thin films of H2O [293,294] and CF4 [295]. In both cases, following the electron-induced dissociation of the molecular adsorbate, a new XPS signal associated with the chemisorption of either O or F onto the Si surface was observed and an effective cross section for chemisorption was then calculated. This cross section for electron-induced chemisorption of oxygen from an H2O bilayer onto a hydrogen-passivated Si(l 11) surface is shown in Fig. 24 as a function of Ei [293,294]. The low energetic threshold for the chemisorption process (i.e., 5.2 eV) has been interpreted as due to the formation of OH via the DEA process... 

The interaction of an electron with a surface produces at least three phenomena which are important in a plasma environment. They are (1) chemical reactions between gas phase species and a surface where electron bombardment is required to activate the process, (2) electron-induced secondary-electron emission, and (3) electron-induced dissociation of sorbed molecules. A fourth phenomenon — lattice damage produced by energetic electrons — depends sensitively upon the properties of the material being bombarded, and, it is important in specialized situations, but it will not be discussed in this paper. 

The cross sections for ESD processes on most surfaces are usually much smaller than cross sections for comparable gas phase processes involving electron-induced dissociation and dissociative ionization . This may be a consequence of the fact that many fragments remain adsorbed on the surface and/or that non-radiative processes such as those described in Sect. 2.1.1 cause the molecule to de-excite before it dissociates. For 100 eV electrons, typical cross sections for gas-phase dissociation are 10 cm (see Ref. 150). For most adsorbates, cross sections lie in range of 10 to 10 cm. A few examples of higher cross sections for adsorbed layers are known, and many examples of smaller cross sections exist. 

Madey TE, Lu QB. Giant enhancement of electron-induced dissociation of chlorofluorocarbons coadsorbed with water or ammonia ices implications for... 

Table 21-4. The relative electronic energies (AEr) and free energies (A( I)) at 298 K of stationary points on the reaction path leading from the radical anions (Y -dXOMPII Y = 3, 5, X=C,T) via transition states (TS) to the C3 -0 and C5 -0 bond broken complexes (Product complex) for electron induced dissociation of pyrimidine nucleotides. All values given in kcal/mol. (Table 2 of ref. [79] (Reprinted with permission. Copyright (2006) National Academy of Sciences, U.S.A.) and Table 1 of ref. [80] (Reprinted with permission. Copyright 2006 American Chemical Society.))...

These results have profound effects for the selective catalytic dehydrogenation of cyclohexane to benzene, a prototypical hydrocarbon conversion reaction. On Pt(lll), the intermediates, cyclohexene and a species, have been identified and the rate constants for some of the sequential reaction steps measured [56]. Adsorption and reaction studies of cyclohexane [39], cyclohexene [44], 1,3-cyclo-hexadiene [48], and benzene [39] on the two Sn/Pt(lll) alloys provide a rational basis for understanding the role of Sn in promoting higher selectivity for this reaction. One example of structure sensitivity is shown in Fig. 2.7, in which a monolayer of cyclohexyl (C H ) was prepared by electron-induced dissociation (EID) of physi-orbed cyclohexane to overcome the completely reversible adsorption of cyclohexane... 

Bazin, M., S. Ptasinska, A.D. Bass, L. Sanche, E. Burean and P. Swiderek. 2010. Electron induced dissociation in the condensed-phase nitromethane II. Desorption of neutral fragments. J Phys Condens Matter 22 084003. 

Yoo HJ, Liu H, Hakansson K. Infrared multiphoton dissociation and electron-induced dissociation as alternative MS/MS strategies for metabolite identification. Anal Chem 2007 79 7858-7866. 

A Dalton is defined as l/12tli of the mass of a C atom. It differs from an atomic mass unit (amu), which is defined as l/16th of the mass of a atom. Electron capture dissociation Electron detachment dissociation Electron-induced dissociation... 

Lioe, H. O Hair, R. Comparison of collision-induced dissociation and electron-induced dissociation of singly protonated aromatic amino acids, cystine and related simple peptides using a hybrid linear ion trap-FT-ICR mass spectrometer. Analytical and Bioanalytical Chemistry 2007, 389, 1429-1437. 

Electronic Excitation Dissociation (EED) and Electron-Induced Dissociation (EID)... 

Figure 16.1. Typical ranges of activation times associated with various activation methods in tandem mass spectrometry. EID, electron-induced dissociation SID, surface-induced dissociation CA, collisional activation (beam), typical conditions used in a beam-type tandem mass spectrometer ICR-SORI, ion cyclotron resonance sustained off-resonance irradiation cw IRMPD, continuous-wave infrared multiphoton dissociation. (Reproduced from Ref. 15 with permission from John Wiley Sons.)...

Product ions observed from irradiation of singly charged cations with moderate energy (10-30 eV) electrons may also be a consequence of direct vibrational or electronic excitation—that is, an EIEIO process. This process, depicted in Eq. (16.16a), may also be referred to as electron-induced dissociation, Recent work by Lioe and... 

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