Synchronous diagonal

Between these two idealised extremes there then exists a practically continuous scale of cases corresponding to the majority of real situations, where the asynchronisation in the formation of bonds is only partial. Since the degree of this asynchronisation is given by the detailed form of the corresponding line, it is apparent that the extent of the deviations from the ideally synchronous diagonal line or the closeness of the approach to the ideally nonconcerted two-step line provides a simple means of characterising the concertedness and/or non-concertedness of the reaction. In spite of its conceptual simplicity, the above... 

Fig. 4 A transition state for phosphoryl transfer in which bond fission is ahead of bond formation to the phosphoryl acceptor (nucleophile) is loose, and resides in the lower right region. In the reverse situation a tight transition state results in the upper left region. If the sum of bond order to nucleophile plus leaving group is unity, the transition state will lie on the synchronicity diagonal.

This scheme includes ET rate constants only for the d - d electron-transfer processes, in which the system conformation is conserved, and conformational and ET steps only occur sequentially. Intuitively, it might be expected that the kinetic scheme must include ET that is synchronous with a conformational change in the medium coordinate. However, we showed [10a] that it is not necessary to include the diagonal processes (e.g., A Ig) when considering stable substates. 

The synchronous spectrum (Fig. 3-31 A) is symmetric with respect to the diagonal line corresponding to coordinates vi = V2. Several peaks (A, B, C and D) on this line are called autopeaks which are always positive. The stronger the peak, the larger the variation of its band intensity due to external... 

The term synchronous is reserved to denote a mechanism where formation and fission occur to the same extent in the transition structure of a concerted mechanism the transition structure is anywhere on the diagonal dashed line (Figure 1). Bond order balance can be deduced from the changes in effective charge in the transition structure provided the charge is defined by the same standard dissociation equilibrium. This is illustrated by the displacement reaction of pyridines on 7V-phos-phopyridinium species (Scheme 4) the standard equilibrium for both bond formation and fission is the dissociation of substituted pyridinium ions (XpyH ) and hence the effective charges can be directly compared for both processes. 

Within the context of Fig. 17.2, HAT is the special case of the diagonal path. The electron and proton can transfer more or less synchronously along the same physical coordinate (r and tp), in which case there is no development of polarization to couple to the solvent. The reaction then follows the diagonal path in Fig. 

We have noticed, that near the period-doubling bifurcation self pulsations appear, which are close to the diagonal in the space (01,02), cf. Fig. 6.9, orbit A. Such pulsations appear when there is no phase shift between the amplitudes oi and 02 of the lasers, cf. Fig. 6.9(A). On the contrary, near the Hopf bifurcation, we observe that self pulsations are close to the antidiagonal . Such a phenomenon was reported in Ref. [20] and called inverse synchronization . In this case, oi is shifted with respect to 02 by a half of the period, cf. Fig. 6.9(C). The orbit B in Fig. 6.9 corresponds to the intermediate regime. In the following two sections we consider these phenomena in more detail and show that the phase propagation parameter ip determines the possibility to observe identical or inverse amplitude synchronization. 

In a synchronous 2D map, the peaks located in the diagonal (autopeaks) correspond to changes in intensity induced in our case by temperature, and are always positive. The cross-correlation peaks indicate an in-phase relationship between the two bands involved. 

FIG U RE 10.13 (a) EEM of an estuarine EA sample and (b) synchronous spectra of the same sample, at different values, which are indicated in the EEM it is seen that synchronous spectra correspond to diagonal cuts on the EEM. (Reprinted from Chemosphere, 58, no. 6, Sierra, M. M. D. et al., Fluorescence fingerprint of fulvic and humic acids from varied origins as viewed by single-scan and excitation/emission matrix techniques, 715-733. Copyright 2005, with permission from Elsevier.)... 

The correlation intensity at the diagonal position of a synchronous 2D spectrum (Figure 1-10) corresponds to the autocorrelation function of perturbation-induced... 

Figure 1-18 shows the synchronous 2D IR spectrum of the blend. Autopeaks observed on the diagonal positions of the spectrum near 1454 and 1495 cm represent the strain-induced local reorientation of polystyrene phenyl rings. The 1454-cm band also contains a contribution from CH2 deformation of the backbone of polystyrene [10, 11, 51]. A pair of intense cross peaks appear at the off-diagonal positions of the spectral plane near 1454 and 1495 cm , indicating the existence of a strong synchronicity between the reorientation of transition dipoles associated with these two IR bands of polystyrene phenyl side groups. 

---