Eneigy diagram

Fig. S.l. Potential eneigy diagram for nucleophilic substitution by the ionization (S l) mechanism.

The usual way to visualize a junction is to draw an eneigy diagram that shows the bottom of the conduction band Er and the top of the valence band Ev as a function of distance. The so-called band curvature that appears at both sides of the junction interface reveals a variation in the potential with a distance in the direction perpendicular to the junction surface. The formation of an MS barrier is depicted in Figure 14-1. 

La photovoltaic cells, the same redox reaction, OX + e = KED, may be used for both the anode and the cathode. Figure 10-33 shows an eneigy diagram of an operating photovoltaic cell this cell consists of a metallic cathode and a photoexcited n-type semiconductor anode. The electromotive force (the open cell voltage), ph > approximately equals the difference between the flat band potential of... 

Figure 2-10 Eneigy diagram illustrating the temperature change in a reaction in which no heat is exchanged with the surroundings, a situation called an adiabatic reactor.

In an exactly analogous but opposite manner, doping germanium with arsenic (five valence electrons) results m an excess of electrons and a donor (the arsenic donates the fifth electron or n-type (n = negative electrons) semiconductor. The conduction can be viewed in terms of an eneigy diagram in which the electrons can be removed from the impurity arsenic atoms to the conduction band of the semiconductor (Rg. 7.27). 

Fig. 14.4 Surface-free eneigy diagram (/) of RuSc2 versus the chemical energy (jt) of Ru, involving low-index surfaces (conf.l to conf.5). The darker region is the existence of Ruj Se, cluster-like nanoparticles, given by A/

FIGURE 8.18 This eneigy diagram for the same reaction shown in Figure 8.17 emphasizes the reversal. Here the activation energy for displacement of cyanide hy iodide is shown. 

PROBLEM 8.25 Select the animation tided Unimolecular elimination El and observe the energy diagram. Do you suppose this reaction is reversible Use the eneigy diagram to answer this question. Use the nature of the products to answer the same question. 

PROBLEM 8.28 Observe the Hofmann elimination reaction. Draw the eneigy diagram shown for the reaction. Draw a new reaction curve for the same reaction run in a more polar solvent. Draw the curve for a reaction run in a less polar solvent. Which solvent would likely give the faster Hofmann elimination ... 

Fig. 13.13 Poieniial eneigy diagram for a pholochemically induced honwnuctear eleciron transfer in a mixed valence complex (R = reactants ...

Figure 6 (a) Reaction eneigy diagram for DME formation via a surface methoxy intermediate involving one methanol molecule at each step... 

It is seen from the eneigy diagram that the highest potential barrier is attributed to the transformation of the long-lived complex A2 into the long-lived complex A3. Nevertheless, this barrier also lies below the minimum eneigy of the reactants. In die activated complex A3 4= the N(ij— H(2) and N(2>—O bonds are cleaved to form H2O and N2. It is clear that the reaction should proceed through channel b when the H(2>— O and N(2)—O bonds are cleaved. 

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