Initial-state energy

The change of the initial state energy of the silver core levels during size reduction clearly suggests that there should be size dependent changes in the valence band DOS of the Ag nanoparticles, which can be visualized by valence band XPS and UPS measurements. 

The reaction rate constant is determined with statistic averaging of transfer rate w( ) across the initial-state energy spectrum. When this spectrum is continuous, the averaging comes down to integration [6, 7] ... 

Constant initial state techniques require the photon energy and electron energy analyser to be scanned synchronously so that hv — E is kept constant. In this way, the photon energy dependent partial yield of electrons in an energy window AE at a fixed initial state energy E = E — hv is measured. Core level to empty surface state transitions are enhanced by selecting the appropriate E corresponding to a minimum in the valence band emission. 

An interesting situation arises in mixed solvents that are predominantly aqueous. A small addition of, for instance, alcohol, enhances the hydrogen-bonded structure, whereas at larger alcohol concentration, the structure breaks down and the solvent becomes nonaqueous (54). In the range of small ethanol concentrations, J// of the 5 1 solvolysis of t-butyl chloride has been compared (7, 8) with the heat of solution of that substance on the one hand, and with the heat of solution of salts of comparable molecular size, assumed to resemble the transition state, on the other. It is concluded (8) that it is the initial state energy and not that of the transition state which is influenced by the structure of the solvent. 

Let us modify the difference of potential between electrode and electrolyte from a value A< ). The energy of final state does not vary, whereas the initial state energy is modified from the quantity -FA (j). The conditions for the reaction are the same as before (curve 3), however the summit of the energy curve only increases from a value -aFA( >, because the shape of the energy curve. 

Figure 1.6 A schematic potential energy surface for an arbitrary surface reaction. The nomenclature is = reference energy chosen to be zero, initial state energy, rs = transition state energy, ps = final state energy, a = activation energy barrier, Ai = energy change of the reaction.

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