Slow electrons generation

When samples with no chemically reducible constituents (guest species) are investigated, then the method of charge compensation can be appUed by a flood of slow electrons generated in a flood gun (essentially a glowing filament with a small extraction potential accelerating electrons with about 50 eV onto the... 

Reduction of inorganic oxides can also be provoked during XPS analysis. For instance reduction of CuO has been demonstrated to be due to both slow electrons generated from the X-ray window (nonmonochromatic source) and photoelectrons produced in the sample. 

Yamamoto also explored triphenylamine core dendrimers of the form Corei7-Rpti2-Periph15.125 In this system, the redox process studied was the oxidation of this core moiety. They showed that as the generation of the dendrimer increased from 1 to 4, the shape of the CV broadened, indicating slowing electron transfer kinetics. 

Fast generation of the radical ions can be attributed to electron-transfer reaction from the singlet excited state and slow radical generation to that from triplet excited state. Fluorescence of both 326 and 327 was quenched in the presence of CCI4 according to the Stern-Volmer equation. The Stern-Volmer constants were estimated to be 1.55 and 17.7 M 1 for 326 and 327, respectively, and quenching rate constants were estimated to be 1010 and 2.7 x 1010 M 1 s 1. 

Combination of UV/Ti02 and ozone is also possible. Ozone acts as a powerful oxidant in place of oxygen, which has a slow electron transfer from Ti02 (reaction 67) [33,119]. In the presence of Ti02, ozone generates HO through the formation of an ozonide radical in the adsorption layer ... 

In particular, O2 adsorbed to Ti02 can be reduced by e, generating in a thermodynamically feasible but rather slow electron transfer reaction (Hoffmann et al., 1995). Values of (02/02 )= —0.3 V and (02/H02) = —0.05 V have been reported for homogeneous solutions the reduction potentials onto the Ti02 surface are probably less negative. As the following set of equations indicates, this cathodic pathway is an additional source of hydroxyl radicals ... 

Fig. 1. Spectral evolution of the hot s-like state of hydrated electron generated in two 6.2 eV photon ionization of light water. The arrows indicate the trends observed in the direction of longer delay times of the probe pulses. Panel (a) demonstrates the evolution between 500 fs and 1.2 ps, showing considerable blue shift and fast decay of the IR features. Panel (b) shows the slow relaxation regime that is observed after 1.2 ps (note the logarithmic scale). In this regime, the band maximum is locked within 20 meV and the spectral evolution is due to relatively slow, isotope sensitive narrowing of the spectral envelope on the red side of the spectrum. This narrowing is likely to be caused by vibrational relaxation of the hot s-like state. See Ref 28 for more detail.

Photoinduced electron transfer from dilferent electron donors to the triplet excited states of Ceo and C70 occurs efficiently and is typically associated with a small reorganization energy [18, 19, 21-27]. Consequently, the occurrence of fast electron-transfer events involving the fullerene excited states has been well established as giving rise to small intrinsic barriers. In contrast with the fast electron-transfer reactions of the triplet excited state of Ceo, an extremely slow electron-transfer reaction has been reported for the reaction of Ceo in its ground state with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to produce Ceo in benzonitrile. The latter can be followed even by conventional Vis-NIR spectroscopy [28]. In this instance, however, it is not clear whether the generation of Ceo is directly related to electron transfer from DBU to Ceo, or if Ceo evolves from the produet of a secondary reaction. 

Table I shows that hydroxyl radicals react rapidly with both monomers examined. High rate constants would also be expected for other monomers. Hydrated electrons do not react rapidly with ethylene, but a slow reaction cannot be excluded. Hydrated electrons react with other monomers with rate constants around 1-2 X 1010M-1 sec."1. A similar high reactivity would be expected for unexamined vinyl monomers. There is no reason to suppose that the hydration of the electron plays an important part in the reaction hence, electrons generated by radiation in other media should also react with vinyl monomers. For vinylpyridine, comparison of the neutral form with the protonated form shows a significantly higher rate constant for reaction with the protonated form, but other such comparisons (where possible) have not yet been made.

Ar/CHz/i) flows through the cell, the gas becomes ionized. The slow electrons formed flow to the anode, thus generating a current. 

The rate enchancement of CO insertion into metal-carbon electron compounds was demonstrated for (39). While normally CO insertion and formation of fluorenone is very slow, electrochemical generation of a 19-electron anion greatly facilitates the insertion process. ... 

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